ZOOLOGISCHE MEDEDELINGEN
UITGEGEVEN
DOOR H E T
RIJKSMUSEUM V A N NATUURLIJKE
(MINISTERIE V A N C U L T U U R , R E C R E A T I E
HISTORIE
TE
LEIDEN
E N MAATSCHAPPELIJK
Deel 41 no. 11
WERK)
27 juli 1966
THE PATTERN OF DERMAL-VERTEBRAL
C O R R E L A T I O N IN S N A K E S A N D A M P H I S B A E N I A N S
by
A . A L L A N A L E X A N D E R ) and C A R L G A N S
1
Department of Biology, State University of New York at Buffalo,
Buffalo, N . Y . 14214, U.S.A.
INTRODUCTION
It has long been known that the arrangement of external scales retains a
constant relation to the primary pattern of mesodermal segmentation. T h e
ratio of the number of dermal scale rows or annuli to the number of vertebrae has, therefore, been considered to be of fundamental importance in
squamate classification (Stehli, 1910; Camp, 1923). Yet the difficulty of
determining it has fostered the presentation of hypotheses based on relatively
few total counts; some such hypotheses have relied upon comparisons made
by dissection along limited portions of the trunk. The general implication
communicated by the many statements in the literature has been that the
ratios are constant at the generic or familial level, that the ratios ordinarily
represent simple, whole number relations (i.e. 1 : 1, 1 : 2, 2 : 1), and that
the scale-vertebra relation is constant along the length of the body.
Authors have disagreed regarding the presumed evolution of these regularities; thus Stehli (1910) argued that the 1 : 1 ratio was primitive, while
Camp (1923) considered it to be most highly advanced. The most "primitive"
snakes (Bellairs & Underwood, 1951) were generally stated to have a 2 : 1
and the "advanced" forms a 1 : 1 ratio. In contrast, the presumably most
primitive amphisbaenid (Smalian, 1884) has generally been stated to have
a 1 : 1 and all other, and presumably more advanced, forms, a 2 : 1 ratio.
A recent report (Gans & Taub, 1965) showed a simple method of determining these ratios, emphasized that the ratios varied markedly at the species
1) Present address : Department of Biology, Canisius College, Buffalo, N . Y . 14208.
172
ZOOLOGISCHE M E D E D E L I N G E N 41 (1966)
level, and also showed that the relationship of scales to vertebrae within
the Typhlopidae was not a simple, whole number ratio. This suggested the
desirability of checking the actual values on which the various rules had
been established.
W e are grateful to Drs. Neil D . Richmond and H . W . Parker for volun­
teering information on aspects of this problem, and to D r . E . E . Williams
for reading the manuscript. The specimens examined were loaned by C.
M . Bogert and R . G . Zweifel of the American Museum of Natural History,
New Y o r k ( A M N H ) , A . E . Leviton of the California Academy of Sciences
( C A S ) , the Carl Gans collection at Buffalo ( C G ) , Ν . D . Richmond of the
Carnegie Museum, Pittsburgh ( C M ) , H . M a r x and R . F . Inger of the
Chicago Natural History Museum ( C N H M ) , A . R . Hoge of the Instituto
Butantan, Sao Paulo ( I B ) , F . W . Braestrup of the Universitetets Zoologiske
Museum in Copenhagen ( K M ) , J. A . N . Cranwell and J . M . Gallardo of
the Museo Argentino de Ciências Naturales in Buenos Aires ( M A C N ) ,
E . E . Williams of the Museum of Comparative Zoology ( M C Z ) , M . Boese­
man of the Rijksmuseum van Natuurlijke Historie, Leiden ( R M N H ) , H .
Wermuth of the Staatlichen Museum für Naturkunde, Stuttgart ( S M N S ) ,
C. F . Walker of the University of Michigan Museum of Zoology ( U M M Z ) ,
D . M . Cochran of the United States National Museum ( U S N M ) , and J .
Eiselt of the Naturhistorisches Museum, Vienna ( V M ) . D r . J . C. List
kindly permitted us to cite data from his (unpublished) thesis. This study
is supported by a grant from the National Science Foundation GB-2460
(to C. Gans).
METHODS
The arrangement and numbers of scale rows, or annuli, on the dorsal
and ventral surface of trunk and tail, and the numbers of trunk and caudal
vertebrae were determined for some 220 specimens. Similar determinations
were accomplished on 130 specimens of Blanus. Additionally, determinations
on some 100 other specimens recorded by Gans & Taub (1965), Gans &
Laurent (1965), and by List (1956, unpublished thesis) were also used in
the analysis. The ranges of observed values are shown by species in table 1
for the amphisbaenids, and in table 2 for the "primitive" snakes and a few
advanced snakes.
The forms sampled include the 23 recognized genera of amphisbaenids,
fifteen genera of primitive snakes, and various advanced snakes. The various
ratios observed in each family or other grouping are shown i n table 3.
The numbers and proportions of vertebrae were determined fom X­rays
taken with an unfiltered 60 K V P dental unit at 3.5 ma on Kodak Type A A
A L E X A N D E R & GANS, D E R M A L - V E R T E B R A L C O R R E L A T I O N
173
industrial film ; the target to film distance was 50 inches. A l l determinations
were made under a dissecting microscope. Measurement of proportions obviously had to be restricted to those vertebrae X-rayed while lying with their
long axis in parallel to the film. Hypaque and fine steel pins were used
to indicate the position of dermal segments relative to skeletal structures.
Checks indicated that the counts of dermal and vertebral elements along
the trunk were repeatable with less than 1% error. Caudal structures, particularly in short-tailed forms, are markedly reduced in size and the vertebrae
are often partially fused. The differences between repeated counts here approached 10%. Correlation of caudal dermal and vertebral elements also
poses a problem, particularly in the typhlopids. Here the tail is short, sharply
curved, and composed of smaller vertebral elements. Additionally the X-rays
suggest that the soft tissues may shift (possibly post-mortem) so that the
cloacal slit may, in a given species, fall anywhere from the third caudal to
the fourth from last trunk vertebra. It may be that this accounts for some
of the apparently aberrant ratios ; otherwise it may be that species differences
are being dealt with.
RESULTS
Serpentes
Trunk proportions. — Neither the length of the dermal segments nor of
the vertebrae remains constant throughout the trunk region. The changes
are gradual, but quite evident when comparisons are made between regions.
Both scales and vertebrae of the nuchal-pectoral and precloacal regions
are generally of equivalent length, and definitely shorter than those of the
midthoracic region. The lengths of the scales and vertebrae generally change
in parallel, maintaining a constant relationship along the trunk, and giving
rise to the described simple, whole number ratios (i.e. 1 : 1, 2 : 1, etc.). This
is in accord with the expected basic embryological relationships of the dermal
and vertebral elements. In a few forms, the constancy of the relationship is
disrupted by (seemingly secondary) changes in the dermal elements, changes
that result in deviant ratios.
Richmond (in litt.) commented on the marked regional differences in
scale size seen in certain typhlopids. Yet the vertebral column of these forms
shows the same regional proportions described above for other snakes, except perhaps for a shorter precloacal region, and a sharp change in the length
of vertebrae between the thoracic and precloacal zones. The dermal elements
also increase in length along the trunk, but seemingly with no corresponding
decrease in the short precloacal region. The degree of increase appears to
be species specific.
174
ZOOLOGISCHE M E D E D E L I N G E N 41
(1966)
The hydrophiid Laticauda laticaudata shows the "normal" dermal and vertebral proportions. The two specimens of Lapemis hardwicki, which differ
so drastically that there is some doubt whether they are indeed conspecific,
show variation in dermal, but not vertebral proportions. One specimen ( M C Z
23755) shows an increase in dermal length between the nuchal-pectoral and
midthoracic regions, that is followed by a decrease posteriorly in the region
leading to the relatively small precloacal and caudal scales. The other specimen ( M C Z 20647), however, shows little change of length of the dermal
elements throughout the trunk region; the elements of the nuchal-pectoral
are equal to or even slightly greater than those of the midthoracic zone.
Trunk ratios. — Bellairs & Underwood (1951) stated that various modified burrowing snakes of the families Typhlopidae, Leptotyphlopidae, and
Uropeltidae always have a ratio of transverse ventral rows to vertebrae of
2 : 1 , and that these thus differ from all other snakes which always have
a ratio of 1 : 1. This statement led Williams (1959) to the conclusion that
the uropeltids had not been directly derived from Cylindrophis (Aniliidae)
or its immediate relatives, despite much evidence demonstrated by him to
the contrary.
Comparison of the data given in table 3 shows clearly that snakes, except
for members of the genera Typhlops, Helminthophis, Anomalepis, and Liotyphlops, always have a 1 : 1 ratio between the number of enlarged ventral
shields and of vertebrae. The literature statements regarding the departure
from this ratio by members of the Leptotyphlopidae and Uropeltidae are
thus in error.
In the Typhlopidae (sensu lato) the ratios vary from 1.5 : 1 to 2.3 : 1.
However, as already pointed out by Gans & Taub (1965) and suggested in
List's unpublished thesis the values (1) ordinarily do not represent simple,
whole number ratios, (2) generally depart significantly from 2 : 1, and (3)
are species specific.
The comparison of dermal and vertebral proportions for three of the
typhlopid species (T. congestus, T. reticulatus, and T. sp., a yet unidentified,
large African form) indicates that within the nuchal-pectoral region the dermal-vertebral ratio is constant at 2 :1. Thus the overall deviation from this
ratio for the species (1.75 to 1.9 : 1 ; 1.5 to 1.75 : 1, 2.1 : 1, respectively)
is due to differences primarily in the midthoracic, but also in the precloacal
region.
A different situation exists in boid snakes. It has long been known (cf.
de Witte, 1962; Gans & Laurent, 1965) that some of these have dorsal scales
that are much smaller and hence shorter (when measured along the snake's
axis) than the widened ventral shields. This implies that there must be more
A L E X A N D E R & GANS, D E R M A L - V E R T E B R A L CORRELATION
175
dorsal than ventral scales along the length of the trunk. The present ob­
servations confirm this and also show that there are "additional" scales in­
volved, since the correlation between the number of ventral shields and that
of vertebrae is more regular. A similar case may exist within the colubrids,
as a figure of the nuchal region of a specimen of Spalerosophis cliffordi
(Barash & Hoofien, 1956) shows multiple dorsal scales corresponding to
the enlarged ventrals.
O n the other hand, Parker (1940) reported that within the colubrid genus
Thrasops, T. flavigularis is unique in possessing dorsal scales whose length
is nearly twice that of the ventrals. The two specimens of that species viewed
here show dorsal scale to vertebrae ratios of 0.59 :1 and 0.78 : 1. The ventral
scale ratios are 1 : 1, as are both the dorsal and ventral ratios in the other
species of Thrasops.
Only four boid genera, among them the peculiar Tropidophis, do not show
the size reduction and numerical increase of dorsal scales. Casarea, recently
(Parker, 1965) placed in the Bolyeridae, shows the more typical boid pattern.
The snakes of the family Acrochordidae have the body covered by nume­
rous small scales, most projecting into a pointed, posteriorly curving hook.
The ratios are constant along the body and along the tail, though the number
of scales is much larger than that of the vertebrae.
Within the hydrophiids, the specimen of Laticauda laticaudata has 1 : 1
ratios both dorsally and ventrally. The two specimens of Lapemis hardwicki,
however, show both dorsal and ventral scale patterns and ratios which are
quite irregular, and which vary considerably between the two specimens. In
one the dorsal and ventral ratios are ^ 1 . 3 : 1 and 1.1 : 1, respectively, while
those of the other specimen are ^1.8 : 1 and 1.4 : 1. The tail ratios, 1.1 : 1
and 1.2 : ι, in the two specimens are quite similar.
Caudal region. — W i t h two exceptions all forms show a 1 : 1 ratio of
dermal segments to vertebrae along the tail. One exception is formed by the
two species of the genus Helminthophis, the other by some species of
Typhlops. The occurrence in the latter has been commented upon. In the
specimen of Boa, the number of dorsal, but not of ventral segments is larger
than the number of vertebrae. Here again, supplementary dorsal segments
are being dealt with.
Amphisbaenia
Trunk proportions. — The majority of the amphisbaenids examined show
a regional variation of vertebral length that is similar to that found in most
snakes. In general, there also occur changes in the lengths of the dermal
176
ZOOLOGISCHE M E D E D E L I N G E N 41
(1966)
elements corresponding to those in the vertebrae, resulting in simple, whole
number dermal-vertebral ratios.
In a few forms deviations from the normal pattern do exist; such deviations occur most often in the nuchal-pectoral region. The most extensive
deviations occur in four genera where the nuchal-pectoral vertebrae are
significantly longer than those of the midthoracic region. The differences
vary from approximately 5 % in Leposternon to 15 to 2 0 % in Monopeltis,
Tomuropeltis, and Mesobaena. Although corresponding changes in the length
of the dermal elements seem to occur in Mesobaena, there are no such changes
in the other three genera.
Representatives of three other genera, Ancylocranium, Bronia, and Rhineura, show similar, but less extensive modifications. Here, the length of
the nuchal-pectoral vertebrae is equal to that of the vertebrae of the midthoracic region. These forms show corresponding changes in the dermal
elements. A fourth form, Cadea palirastrata, shows the same general pattern
of vertebral lengths, but while the dermal elements of the ventral surface
concur with this, those of the dorsal surface vary further. This variation
occurs within the midthoracic region where there seems to be a decrease in
the length of the annular segments.
The second, and presumably more primitive species of the genus, Cadea
blanoides, shows "normal" proportions of vertebrae and dermal elements of
the dorsal surface. Ventrally the dermal proportions change, with the most
marked changes concentrated in the precloacal region.
A l l other amphisbaenids show "normal" vertebral and dermal proportions.
Trunk ratios. — In the Amphisbaenia the skin is subdivided into so-called
dermal annuli that are separated by inter-annular grooves that ring the body.
In most species there are clearly defined lateral sulci which divide the annuli
into subequal dorsal and ventral half-annuli. Correlation of number of dermal
annuli with that of vertebrae is complicated since a certain number of anterior
body annuli extend over the posterior aspect of the skull. It is thus not the
first, but for instance the sixth to eighth annulus in Blanus, that corresponds
to the position of the atlas.
Allowing for this, there are some four groups of ratios between number
of ventral half-annuli and vertebrae. (1) The two species of the genus
Blanus always show a ratio of 1 : 1 between the number of body annuli
and that of vertebrae. (2) The species of the presumably primitive ( V a n zolini, 1951 ) genera Bipes and Cadea show values between 1.2 and 2 : 1 .
( 3 ) Members of the "advanced" rhineurine genera Leposternon, Monopeltis,
and Tomuropeltis (but not of the genus Rhineura) show a ratio equal to sig-
A L E X A N D E R & GANS, D E R M A L - V E R T E B R A L CORRELATION
177
nificantly greater than 2 : i . ( 4 ) A l l other species, including the bulk of the
members of this group, have a simple ratio of 2 : 1.
Most amphisbaenids have the same number of dorsal and of ventral halfannuli. Where intercalated half-annuli occur, they are almost always dorsal.
Their number is generally low along the trunk, though many species have
one or more over the back of the skull or in the cloacal region. The frequency
of dorsal intercalated half-annuli is generally less than 2 % , only in a few
populations of Amphisbaena innocens have values up to 10% been reported
(Gans & Alexander, 1962).
The two species of Bipes and the two specimens of Cadea are then unique
in possession of a significantly greater number of dorsal half-annuli than
ventral. In Bipes, the ratio of dorsal half-annuli to vertebrae is 2 : 1, sug­
gesting that the ratio of ventral to vertebrae may represent secondary re­
duction. In Cadea the dorsal ratio is slightly less than 2 : 1 for the least
specialized, and somewhat more than 2 : 1 for the most specialized species.
Cadea is the only amphisbaenid genus with very poorly expressed lateral
sulci. The contact region between dorsal and ventral half-annuli is charac­
terized by multiple and irregular interdigitations, yielding a confusing pattern,
and making correlations difficult.
Caudal region. — The vast majority of species have a ratio of 1 : i between
the number of caudal annuli and vertebrae. Exceptions to this are found
only in one of the species of Cadea and both species of Bipes.
In Cadea palirostrata, the departure from 1 : 1 is restricted to the dorsal
surface of the tail, where it ranges from 1.3 to 1.6 : 1. It is clearly due to
the intercalation of additional dorsal half-annuli. In Bipes the departure
from a ι : ι ratio occurs both dorsally and ventrally, though the dorsal ratio
is again larger in one of the two species.
DISCUSSION
The present survey provides evidence that the regional changes i n the
lengths of the dermal and vertebral elements are correlated within certain
groups of squamates. The correlation is of two kinds. First, there are the
dermal-vertebral ratios, which appear fixed on various taxonomie levels.
Secondly, there is a general regularity in the relative length of dermal and
of vertebral elements in different groups; departures from this regularity ap­
pear to occur primarily for immediate functional causes.
The dermal-vertebral ratios have traditionally been used in denoting higher
categories of squamates. Certain assumptions concerning these are here shown
to be wrong. The additional evidence simplifies certain aspects of the taxo­
nomie pattern; it also presents some new problems. It is now possible to
178
ZOOLOGISCHE M E D E D E L I N G E N
41
(1966)
generalize regarding the pattern to be expected in these several families,
and to differentiate between basic trends and limited departures from these.
The assumption is that such departures have quite probably been forced
by selective pressures established by secondary adaptive factors.
The pattern exhibited by the serpentes permits a simplification of their
presumptive phylogeny since it suggests that the group is relatively homo­
genous as far as this characteristic is concerned. Most species show a ι : ι
ratio both dorsally and ventrally on both trunk and tail. The clarification of
this point is useful since it permits pursuit of the hypothesis that uropeltids
and aniliids are closely related (cf. Williams, 1959).
The modification of the dorsal skin (ventral, rarely) by variation in the
size and number of scales in certain boids, colubrids and hydrophiids
obviously represents secondary departures from the basic pattern.
A s interesting as the general constancy is the departure from this observed
in the four genera generally combined under the heading Typhlopidae. Their
specialization in this characteristic provides additional evidence for McDowell
& Bogert's (1954) suggestion that the typhlopids are more distinct from
the remainder of the snakes than are the leptotyphlopids. In spite of publica­
tion of the hypothesis that these genera are "lizards", it remains most
plausible to follow the view of List (1956) who states that "these groups have
diverged from each other at an early date, but are derived from a common
ancestor".
The pattern in the amphisbaenids is similarly suggestive. Most of the
species have a 2 : 1 ratio, both ventrally and dorsally, on the trunk and a
ι : ι ratio on the tail. A 1 : 1 ratio on both trunk and tail is found only
in the two species of the genus Blanus. There are numerous other characters
which suggest that this genus is one of the most primitive in the group.
Vanzolini (1951) and Gans (i960) have suggested that the genera Cadea
and Bipes are the next most primitive pleurodont species, while the genus
Trogonaphis is clearly the acrodont form retaining the most generalized
character pattern. Other authors have argued that Bipes represents a distinct
line to be distinguished on the family level.
The primitive status of Cadea and Bipes may explain their distinct patterns.
Bipes is certainly different in that the ventral ratios of both trunk and tail
depart significantly from 2 : 1 , and 1:1, respectively. Cadea is less modified
in that the ventral caudal ratios are regular. Mesobaena, a genus at least super­
ficially similar to Cadea, has the ratios common to most amphisbaenids. This,
and the finding of the 2 : 1 ratio along the dorsal surface of both species of
Bipes, and one of Cadea, and on the ventral surface of the other species of
Cadea, offers at least the presumption that the condition seen in these genera
A L E X A N D E R & GANS, D E R M A L - V E R T E B R A L CORRELATION
179
is not an intermediate or different condition but a secondary modification.
It is highly interesting that the acrodont genus Trogponophis, shown in some
characters to be more generalized than Blanus, has the standard 2 : ι trunk
and ι : ι tail ratios noted in other members of that family.
The increase in the number of dorsal and ventral body half-annuli in the
three rhineurine genera, Monopeltis, Tomuropeltis, and Leposternon, can be
shown to occur in the modified nuchal-pectoral region. Here the vertebrae
are significantly longer than those of the trunk region, whereas the pattern
in the vast majority of species is one in which the nuchal are significantly
shorter than the trunk vertebrae. A s the relative length of the dermal annuli
in the nuchal-pectoral region does not undergo a correlated change, the dermalvertebral ratio approaches 3 : 1 , thus yielding an overall increase beyond the
common 2 : 1 ratio. The increased ratios are thus a secondary result of the
specialized excavating mechanism. O f interest here are the normal ratios
of the genera Aulura and Rhineura. The former is unspecialized, while the
latter evidences a level of specialization approaching that of the other forms.
The results then support other evidence that the grouping may be artificial.
While the present study has simplified the patterns observed within the
snakes and amphisbaenids, it does not provide a clear indication regarding
the evolutionary sequence. In snakes, the two groupings are each sufficiently
old to support the contention that either pattern may have been primitive.
In amphisbaenids, Blanus may or may not retain an "ancestral" condition,
although the finding of a 1 : 1 caudal ratio consistently throughout the am­
phisbaenids suggests that this may be the case.
If the evidence for this 1 : 1 to 2 : 1 sequence be accepted, it would sup­
port Stehli's (1910) contention that the squamate integumentary patterns are
primitively 1 : 1, and upset Camp's (1923) argument in the opposite direction.
There is, however, no reason to suppose that the trend need always go in
the same direction in the various squamate groups.
I
I
I
2
Baikia africana
Bipes biporus
B. canaliculatus
II
2
4
9
Cadea blanoides
C. palirostrata
lig
Bronia brasiliana
Blanus cinereus
B. strauchi
I
Aulura anomala
I
2
Anops kingi
s. somalicum
I
I
I
2
I
2
2
2
I
2
2
2
I
I
Ancylocranium
2
Number of
specimens
Amphisbaena alba
A. angustifrons
A. camura
A. carvalhoi
A. darwini heterosonata
Α. dubia
A. fenestrata
A. fuliginosa
A. leeseri
A. manni
A. mitchelIi
A. munoai
Α. ο. occidentalis
Α. ridleyi
Α. silvestrii
Α. vermicularis
Amphisbaenidae
Species
185­196(200­211)
272­294(306­336)
225­227
ι19­133
98­128
?i54­i6i?(259­260)
165(210)
250(251)
184
229­232(230­232)
197
225­235
215(213)
208­212
264
172
180(178)
229
204­212
190
203
237­245
198
216­226(215­226)
236
205­215(208­215)
223­227
Body
2­3
3­4(3­5)
3
1­3
1­4
4
5
3
5/4
3­4
5
3
4
4
3
2­4
3
2­3
3/4
2
2­3
3
3
3
3­4
2­3
2
Lateral
Ventral annuli (Dorsal) *)
3
2
2­3
105­107
136­145
13­15(16­19)
III
2­4
1­4
ι15­127
92­122
M
12
12­13
18­21
14­20
16­18
22
1­2
I
14
21
19
8
15­17
16?
25­26
18
(Autot)
28
20
26
20
20
28
15­16
14?
5
21
16
Caudal
3
2
3
2
3
2
I
-
2
1­2
2
2­4
2­3
3
2­3
2
2?
2
2?
2
Lateral
129­130
104
126
92
113­114
97
131
87
89
114
108
104­106
?II2­II7?
III­II3
97­98
ι07­112
117?
104­108
93
102
ι19­122?
102­107
Body
Vertebrae
13
10­12
17­22
15­20
21(25?)
30
14
21
18
6
23
17(18)
21
26
14
25
i 6 ( + ι A utot)
(Autot)
27(28)
20
13
6(Autot)
20­21
16
14­16
?II­I6
Caudal
Numbers of segments and vertebrae in Amphisbaenia.
TABLE ι
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5
3
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3
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3
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4
3
4
4
5
2
6
4
Typhlops aluensis
T. ataeniatus )
T. bituberculatus
T. braminus )
T. blandfordi )
T. boettgeri )
T. congestus
T. c. cuneirostris )
T. cuneirostris calabresii )
T. infralabialis
T. lumbricalis )
T. luzonensis
T. platycephalus )
T. polygrammicus )
T. proximus
T. pusillus )
T. reticulatus )
T. reticulatus
T. richardi )
T. rostellatus )
3
3
2
2
15-16
344-353
I
I
9
I
I
3
3
—
—
214-251
—
—
321-343
—
—
349
I
503
?320-343?
—
—
—
435-592
?335-358
—
331
320
503
279
346
371
392-409
321-343
290
213
215-261
II
?7-n?
13
14
IO
16-19
10-13
12
—
—
?7-io?
—
—
10-13
—
—
II
II
—
16
7-11
—
—
—
16-23
18-19
—
—
13
27
14-22
—
15
10
17-20
344-356
457-476(B + C)
16-23
439-589
282-312
11-12
10
435
8
377
9-11
314-334
2i5-248(B + C)
257-302(B + C)
27
II
—
—
I
—
12-22
Dorsal
Caudal
Ventral
—
—
328
Dorsal
Scale rows
382-428
468
467
Body
?388-430?
469
468
—
Ventral
I
I
3
5
34
I
I
I
Liotyphlops albirostris )
L. albirostris )
I
2
I
aspinosus )
specimens
Helminthophis albirostris
H. ternetzii
H. sp.
Anomalepis
Typhlopidae
Species
Number of
Number of scales and vertebrae in Serpentes.
TABLE 2
8-10
16
17
II
7-15
—
Caudal
II
237
200
7
180-182
7-12
ii5-i26(B + C)
I30-I43(B + C)
289
13
169
10
208
10
222
II
193-206
14-16
160-173
7-12
12
158
143
9
6-10
137-155
204
13
10
183
?i75-i8i
?n-i5
297-307(B + C)
219-300
13-15
174-182
IO-II
234-252
207-208
205-233
242
230
173
Body
Vertebrae
183
A L E X A N D E R & GANS, D E R M A L - V E R T E B R A L C O R R E L A T I O N
U
00
tebraí
audal
ό­
?
PQ
u
ï
*c
U
75
Ο
Q
U
75
c
O ­
CM
ΝC
ON
M ^Λ
ON
o?
HH
co
ON T f
I
Tf
HH
-
I
00
CO
C
M
CM
Ο
CM T f CM CM
M 1 co
1 C
CM OO CM
J­,
ο
Q
HH
H?
8
o­
o.
CM
CO
C
O
HH
HH
r
+
PQ
O
vO
co
1
>
LJ
co
o­
o­
o.
Π­.
Ο­.
5
CO
00
CO
CO
CM
HH HH
to
HH
ON
H H
H
H H
H H
H H
H H
H H
H H
H H
H H
H H
H H
H
ro CO
t-t h-i t -i
LTJ
N
N
HH
CO
Tf
O
N
N
Μ
τ­Η ο
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Ο
Tf
^
HH
Ο
4t co
HH
LO
Tf
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5
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M
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Tf
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CM
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CO
Tf
8
LA_J
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ON
2 1 5 I1 ι I
1
co co
νθ νθ
J
Tf
CO
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00
Tf
^
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^
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0
M
H
co
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HH
HH
CO
QN
H
H
i
O
Ο
00
H
CM
Μ
Ν
H HH v i v i
totoONvOcovO
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CM
Ν
I 00
to
HH
ON
C/3
C
CM
Ο
CO
CM CM
VO
t
HH
H
rt
Η
HH
HH
CO
Tf
ε
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m
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3
3
CO
3
TH
^ ^ ^
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3
(Λ
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ft
Leptotyphlopidae
<υ
ft
m
V
CO
rs
73
ft
ο
u
HH
CM
HH
Tf
vo
CM CM
M
O
tO
HH
Tf
CO
<
Anilius scytale
Cylindrophis maculatus
C. rufus
(U
Leptotyphlops conjuncta
L. emini )
L. longicauda
L. magnamaculata )
L. maximus )
L. nigricans )
L. phillipsi
Β
HH??
HH
HH
ΠΗ
νθ
Tf
CO
ON ON
ι
o­
Ο ­
^ r
cO
C
M
CM CMMCM
1 Tf 1 C
g CM 00 CM8! 8
CM C
M
W
CM . ONT ON
co. 00
co
? " co
to
>
υ
00 00
Tf
+
PQ
75
Vi
vO 00
T+ T + T?T°°TT
VO
ο­.
CO
Ό
Ο
Ι Ο
ο.
J, S i ?
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o­
Ν^ Νο ^
PQ
G
HH
ON ON
.Ν
. ON ΝON
CM
CM . ΟON vO
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ν θ vA
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vO co
co . .
ο.
OO
O
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vi
vi
vO
Ι Ο
CO
! ι! ι 1ι
1
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>>
u
CM CM Ν v o
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Ν 00
vO
co
co
Tf
T f O*
VO
T ff
T
t too vO
vO ON
ON . . ν θ
h H
h
H O
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M TT ff H
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1
m
HH
vQ co co
(Ν
I
VU
HH
o­
1
75
"rf
Τ + Τ + ϊ?Το>ττ
Brachyophidium rhodogaster
Melanophidium wynaudense
Platyplectrurus madurensis
Plectrurus perroteti
Rhino phis blythi
R. philippinus
Uropeltis ocellatus
U. pulneyensis
U. rubrolineatus
U. woodmasoni
Scale ]rows
>
^
CM C
M
o­
ri­
HH
t/3
^
Λ CM
?î?
SS
CM CM CM
C
M
ο
PQ
VO
Tf
8*8
>>
7
PQ
Ι Ο
>
νο C
M
ΤΤ 2
Ο co
" ο
~ U
+
+
Lichanura roseofusca
Python (More
l ia) argus
P. sebae
Sanzinia madagascariensis
Trachyboa boul engeri
Tropidophis mel anurus
T. semicincta
Charina bottae
Chondropython viridis
Corallus (Boa) annulatus
Enygrus asper
Epicrates angul ifer
Ε. striatus
Ery'χ col ubrinus
Ε. conicus
Ε. jaciil us
Eunectes notaeus
Liasis antethystinus
L. chil dreni
L. fuscus
Acranthophis
madagascariensis
Aspidiotes mel anocephal us
Boa canina
Β. enydris
Bothrochilus boa
Calabaria reinhardti
Boidae
Xenopeltis unicol or
Xenopeltidae
Species
139
286
287-295
?I82-I84?
188
?168-182?
I
2
2
I
I
I
I
I
I
2
I
2
I
2
2
I
132-135
193-199
204
273
235
268
278
206
230
315-321
281
265
I
I
I
I
I
I
I
I
I
237
294
198
260
264
231
211
236
184-188
Ventral
I
2
specimens
Number of
Scale rows
Dorsal
274
128-132
190-202
210
245
359
606
348
421
254-278
316
200-318 ± 1 0
415
i86±3
413=^=10
433-466
270-277
265
590
385
256
312
39+
24-25+
40-41+
79+
78+
40+
74+
48+
46+
59
113-116+
19+
18?
92-93+
?26-28?
54+
27+
40+
82
86
21 ±
82
Ill
340
470
488
34+
48+
68?
26-30 ?
57+
27+
47+
91
89+
19+
88
III
79
51+
56+
26-32
Dorsal
23-25+
41-43+
39+
42+
81+
109+
75+
52+
48+
92-97+
?26-28?
20+
18?
66
111-114+
Caudal
Ventral
460
184-185
Body
±
2
131-134
196-198 — I
211
283
208
235
276
275
282
174-185
238
318-322 ± 5
290
291-296
187-190
100
215
240 ± 2
268
144
293
203
261
266
236
? 2 4 6 ± 10
187-100
Body
±
44
83±6
86+
S7 i
26+
73
112
34+
48+
26-30 ?
Caudal
24
41
37+
75+
42+
52+
86
48+
76 +
19
65+
n8-ii9± ι
18+
21+
^79+2
91-92
28-29
Vertebrae
4
3
2
x
)
)
)
)
Data
Data
Data
Data
from
from
from
from
Dunn (1941) in List (1956).
Dunn & Tihen (1944) in List (1956).
List (1956).
Gans & Laurent (1965) and Gans & Taub (1965).
Crotalus terrificus
Viperidae
Micrurus sp.
Elapidae
5
) Skull plus a few anterior vertebrae missing.
— data not available.
(B + C ) = total of body plus caudal.
<­n
OO
M
O
>
η
o
>
r
Laticauda laticaudata
W
Lapemis hardwicki
H
M
<
>
M
Ö
>
O
w
ö
>
r
w
X
>
Hydrophiidae
Colubridae
Ahaetulla mycterizans
Dasypeltis scabra
Dlibcrria lutrix
Elachistodon westermanni
Malpolon monspessulanus
Psammophylax tritaeniatus
Thrasops flavigularis
T. j. jacksoni
T. schmidti
T. occidentalis
A crochordus granulatus
Acrochordidae
Casarea dussumieri
Bolyeridae
Species
l86
ZOOLOGISCHE M E D E D E L I N G E N 4 I (1966)
TABLE 3
Dermal­vertebral ratios.
species
Caudal
Body
Number of
Ventral
D orsal
Ventral
Dorsal
Serpentes
Typhlopidae
Anomalepis
Helminthophis
Liotyphlops )
Typhlops )
2
3
3
I
1.8­2.0 : ι
1.9 : I
1.8­2.0 : ι
1.7­2.0 : ι
ι.0­1.7 : ι
ι :I
ι.0­1.7 : I
25
15­2.3 : ι
1.5­2.3 : ι
ι .0­1.5 : ι
ι .0­1.5 : I
7
ι :I
ι : I
ι : I
ι : ι
I
I
I
I
2
4
ι
ι
ι
ι
ι
ι
ι
ι
ι
ι
ι
ι
ι
ι
ι
ι
ι
ι
ι
ι
ι
ι
ι
ι
I
2
ι :I
ι :I
ι :: ι
τ :: ι
ι : I
ι :I
ι : ι
τ : ι
I
ι :I
ι ;: ι
ι : I
ι :ι
I
I
2
I
I
I
I
Î
I
2
ι
ι
ι
ι
ι
ι
ι
ι
ι
ι
ι
ι
ι
ι
ι
I
I
I
ι :.
ι :: ι
ι :: ι
ι :: ι
ι :: ι
ι :: ι
I : ι
ι ;: ι
I : ι
I : ι
ι :: ι
0.9 : ι
ι :: ι
0.9 : ι
0.9­1.0 : ι
I : ι
I : ι
I : ι
1.5 : ι
1.2 : ι
ι : ι
ι : ι
ι :ι
1.1 : ι
ι : ι
ι : ι
0.9 : ι
ι .0­1. ι :: ι
1.0­1.1 : I
ι :ι
ι :ι
ι :ι
0.9­1.5 :: ι
ι : ι
ι : ι
ι : ι
I
—
Leptotyphlopidae
Leptotyphlops )
4
Uropeltidae
Brachyophidium
Melano phidium
Platyplectrurus
Plectrurus
Rhino phis
Uropeltis
:
:
:
:
:
:
τ
I
I
I
I
I
: I
: I
:: ι
:: ι
:: ι
:: ι
: I
: I
:I
:I
:I
: I
:
:
:
:
:
:
ι
1
ι
ι
ι
ι
Aniliidae
Anilius
Cylindrophis
Xenopeltidae
Xenopeltis
Boidae
Acrantophis
Aspidiotes
Boa
Bothrochilus
Calabaria
Charina
Chondropython
Corallus
Enygrus
Ε picrates
Eryx
Eunectes
Liasis
Lichanura
Python
Sanzinia
Trachyboa
Tropidophis
3
I
3
I
2
I
I
2
:I
:I
:I
:I
:: ι
:: ι
:: ι
:: ι
:: ι
:: ι
:I
:: ι
:I
:: ι
:: ι
: ι
: ι
: ι
1.9 : ι
1.6 : ι
1.3­2.5 : ι
1.5 : ι
I.I : ι
1.5 : ι
2.5 : ι
1.6 : ι
1.3 : ι
ι .4­1.5 : ι
1.4 : ι
1.3 : ι
90­1.5 : ι
I : ι
1.3­2. ι : ι
1.3 : ι
I : ι
I : ι
1
187
A L E X A N D E R & GANS, D E R M A L - V E R T E B R A L CORRELATION
Number of
Body
species
Ventral
I
ι :ι
I
47-5-0 : ι
Caudal
Dorsal
Ventral
Dorsal
Bolyeridae
Casarea
1.8 : ι
ι :ι
i.6 : ι
Acrochordidae
Acrochordus
3-4-3-5 : ι
3-9-4.5 : ι
47-5-6 : ι
Colubridae
Ahaetulla
Dasypeltis
Duberria
Elachistodon
Malpolon
Psammophylax
Thrasops
I
I
I
I
I
I
3
ι
ι
ι
ι
ι
ι
ι
:ι
:ι
:ι
:ι
:ι
:ι
:ι
ι :ι
ι :ι
ι :ι
ι :ι
ι :ι
ι :ι
0.6-1 : ι
ι
ι
ι
ι
ι
ι
ι
:ι
:ι
:ι
:ι
:ι
:ι
:ι
ι
ι
ι
ι
ι
ι
ι
:
:
:
:
:
:
:
ι
ι
ι
ι
ι
ι
ι
Hydrophiidae
Lapemis
Laticauda
I
I
?T.I-I.4 : ι
ι :ι
ι.2-1.8 : ι
ι :ι
i.i : ι
ι :ι
i.i :ι
ι : ι
Elapidae
Micrurus
I
ι :ι
ι :ι
ι :ι
ι : ι
I
ι :ι
ι :ι
ι :ι
ι : ι
Viperidae
Crotalus
Amphisbaenia
Amphisbaenidae
Amphisbaena
Ancylocranium
Anops
Aulura
Baikia
Bipes biporus
Bipes canaliculatus
Blanus
Bronia
Cadea blanoides
Cadea palirostrata
Chirindia
Cynisca
Geocalamus
Le posternon
Loveridgea
Mesobaena
Monopeltis
Rhineura
Tomuropeltis
Zygaspis
16
I
I
I
I
2
I
I
I
I
7
I
I
2
I
I
2
2 :ι
2:1
2:1
2:1
2:1
r-; 1.2 : ι
/wi.6 : ι
1:1
2:1
rwi.8 : ι
2 :ι
2:1
2:1
2:1
2.2-2.9 : ι
2:1
2:1
2.0-2.2 : ι
2:1
^2.2 : ι
2:1
2:1
2:1
2:1
2:1
2:1
2:1
2:1
1:1
2:1
1.9-2.0
2.2-2.4
2:1
2:1
2:1
2.2-2.9
2:1
2:1
2.0-2.2
2:1
^2.2 : ι
2:1
:ι
'ι
:ι
:ι
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1:1
ι .2-1.3 : ι
1.4-1.6 : 1
^1.4 : 1
^1.4 : 1
1:1
1:1
1:1
1:1
1:1
1:1
·
^1.3-1.6 : ι
1:1
1:1
1:1
1:1
1:1
1:1
ι .0—1.3 : 1
1.0-1.5 : 1
1:1
1:1
1:1
1:1
1:1
ι : J
1:1
1:1
1:1
1:1
1:1
1:1
1
1
188
ZOOLOGISCHE M E D E D E L I N G E N 41 (1966)
Number of
Body
Caudal
species
Ventral
Dorsal
2
1
1
1
2:1
2:1
2:1
2:1
2:1
2:1
2:1
2:1
Ventral
Dorsal
Trogonophidae
Agamodon
Diplometopon
Pachycalamus
Trogonophis
x
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1 : 1
) Data from Dunn (1941) in List (1956).
2
) Data from Dunn & Tihen (1944) in List (1956).
3
) Includes data from Gans & Laurent (1965), Gans & Taub (1965), and List (1956).
4
) Includes data from List (1956).
— data not available.
L I S T OF SPECIMENS USED
Serpentes
Typhlopidae. — Helmi nthophi s albi rostri s (P eters) : M C Z 25232, 25234. H. ternetzi i
Boulenger : C G 1594. H. sp. : M C Z 67933. Typhlops aluensi s Boulenger : M C Z 73767,
73768, 73769, 73770. T. bi tuberculatus (P eters) : M C Z 32810, 51890. T. congestus
( D u m é r i l & Bibron) : C M 8043, 15213, 15217. T. i nfralabi ali s Waite : M C Z 65990.
T. luzonensi s Taylor: M C Z 79698. T. proxi mus Waite: M C Z 10278, 72081, 72082. T.
reticulatus (Linné) : IB 7207, 8964, 14752, 14758, 14762, 16245 ; U M M Z 55853, 60655,
63235. T. solomonis P arker : M C Z 72083, 72085, 72086. T. torrcsi anus Boulenger : M C Z
53752, 53753- T. sp. : IB 14029, 14030.
Leptotyphlopidae. — Leptotyphlops conjuncta (Jan) : M C Z 52628, 52629, 52630, 52631.
L. longi cauda (P eters) : M C Z 40093, 40094, 40095, 40096. L. phi lli psi Barbour : M C Z
0642, 9643, 9644.
Uropeltidae —Brachyophi di um rhodogaster W a l l : C G 1699, 1700, 1801, 1802, 1804,
1806. Melanophi di um wynaudense (Beddome) : M C Z 24739. Platyplectrurus madurensi s
Beddome: M C Z 18044, 18045. Plectrurus pcrrotcti Duméril & Bibron: M C Z 4178.
Rhinophis blythi Kelaart: M C Z 1319A, 1319B, 34887, 34888, 39816. R. phi li ppi nus
(Cuvier) : M C Z 18034, ^035, 18037, 18038, 48947, plus one unnumbered specimen.
Uropeltis ocellatus (Beddome) : M C Z 3873, 3884, 47288, 47389. U. pulneyensis (Beddome) :
M C Z 1335, 47042, 47043. U. rubroli neatus ( G ü n t h e r ) : M C Z 3850, 3880, 3881, 3911,
47035, 47036, 47037, 47038, 47039, 47040. U. woodmasoni (Theobald) : C G 1693, 1695,
1696, 1697.
Aniliidae. — Ani li us scytale (Linné) : M C Z 2950. Cyli ndrophi s maculatus (Linné) :
M C Z 57192, 57193, 57194, 57195, 34886. C. rufus (Laurenti) : C G 2518.
Xenopeltidae. — Xenopelti s uni color Boie : C G 2713, 2954.
Boidae. —• Acrantophis madagascari ensi s ( D u m é r i l & Bibron) : M C Z 51848. Aspi di otes melanocephalus K r e f f t : M C Z 32808. Boa canina L i n n é : C G 2696. Β. cnydris L i n n é :
M C Z 80858. Bothrochi lus boa (Schlegel) : M C Z 26940. Calabari a rei nhardti (Schlegel) :
M C Z 9237. Chari na bottae (Blainville) : M C Z 63601. Chondropython vi ri di s (Schlegel) :
M C Z 84010. Corallus (Boa) annulatus (Cope) : M C Z 76678. Enygrus asper (Günther) :
M C Z 84012. Epi crates anguli fer Bibron: M C Z 46465. E. stri atus (Fischer): M C Z
A L E X A N D E R & GANS, D E R M A L ­ V E R T E B R A L CORRELATION
189
68573, 68574. Eryχ colubrinus (Linné) : M C Z 30008, 30010. E. conicus (Schneider) :
MCZ 3885. E. jaculus (Linné) : M C Z 32798, 34050. Euncctes notaeus Cope : M C Z 2795.
Liasis amethystinus (Schneider): M C Z 59124, 84013. L. childreni Gray: M C Z 4215.
L. f uscus Peters : M C Z 59125. Lichanura roseof usca Cope : M C Z 29339. Python argus
(Duméril & Bibron) : M C Z 59045. P. scbae (Gmelin) : M C Z 40302. Sanzinia madagascariensis (D uméril & Bibron): M C Z 11811. Trachyboa boulengcri Peracca : MCZ
29249, 29250. Tropidophis mclanurus (Schlegel) : M C Z 44862, 44864. T. semicincta
(Gundlach) : M C Z 18122.
Bolyeridae. — Casarea dussumieri (Schlegel) : M C Z 49135.
Acrochordidae. — Acrochordus granulatus (Schneider) : M C Z 25607, 65573.
Colubridae. — Ahaetulla mycterizans (Linné) : CG 2777. Dasypeltis scabra (Linné) :
CG 0518. Dubcrria lutrix (Linné): CG 2275. Elachistodon westermanni Reinhardt:
C N H M 152140; K M R6401. Malpolon monspessulanus (Hermann) : CG 2486. Psammophylax tritaeniatus (Günther) : CG 2522. Thrasops f lavigularis (Hallowell) : M C Z
8776, 51009. T. jacksoni Günther: M C Z 9276, 40551, 48342. T. occidentalis Parker:
MCZ 49686, 55232.
Hydrophiidae. — Lapemis hardwicki Gray: M C Z 20647, 23755. Laticauda laticaudata
(Linné) : CG 3080.
Elapidae. — Micrurus sp. : CG 3273.
Viperidae. — Crotalus tcrrif icus (Laurenti) : CG 3272.
Amphisbaenia
Amphisbaenidae. — Amphisbaena alba Linné: CG 1331, 3329. A. angustif rons Cope:
CG 3321. A. camura Cope: CG 3322. A. carvalhoi Gans: CG 2833, 2834. A. darwini
heterozonata Burmeister: CG 1341, 2800. A. dubia Müller: CG 2092, 2093. A. f enestrata (Cope): U M M Z 73847. A. f uliginosa Linné: CG 2802, 3086. A. leeseri Gans:
CG 2803, 2804. A. manni Barbour: A M N H 41051, 41078. A. mitchelli Proctor: CG
2764. A. munoai Klappenbach: CG 2768, 2769. A. 0. occidentalis Cope: CG 1660. A.
ridleyi Boulenger: CG 2501. A. silvestrii Boulenger: CG 2718. A. vermicularis Wagler:
U S N M 6035. Ancylocranium s. somalicum (Scortecci) : CG 3035. Anops kingi Bell:
CG 3324, 3325. Aulura anomala Barbour : CG 2766. Baikia af ricana Gray : B M 1964.253.
Bipes biporus (Cope): CG 2538, 2539. B. canaliculatus Bonnaterre: C M 4321. Blanus
cinereus (Valisnieri) : (Alexander, 1966). B. strauchi (Bedriaga) : (Alexander, 1966).
Bronia brasiliana Gray: V M 12346­861, 12346­? Cadea blanoides Stejneger: MCZ
13571, 13572, 13573, 13574· C. palirostrata D ickerson : MCZ 12331, 12332, 12333, 12448,
12449, 12450, 12452, 12453, 12454. Chirindia e. ewerbecki Werner: CG 3326, 3327, 3328.
Cynisca leueura (D uméril & Bibron): CG 2301. Geocalamus acutus Sternfeld: MCZ
41120. Leposternon af f ine (Boettger): V M 12374; Z M U 26267. L. boulengeri (Boett­
ger): B M 1956.1.3.27, 1956.1.3.28. L. crassum (Strauch): V M 12370:3, 12370:4. L.
phocaena (D uméril & Bibron): U M M Z 60518; Z M U 9388. L. polystegum (D uméril):
N H M B 68D ; Z M U 9808. L. scutigerum (Hemprich) : B M 1904.2.2.2; Z M U 1398.
L. wucheren (Peters) : V M 12373 ; Z M U 9389. Loveridgea ionidesii (Battersby) : CG
1830, 1831. Mesobaena huebneri Mertens: C N H M 130987. Monopeltis c. capensis Smith:
CG 1589, 1591. M. guentheri Boulenger: C G 3308, 3309. Rhineura f loridana (Baird) :
CG 2995, 2996. Tomuropeltis pistillum (Boettger) : CG 1588. Zygaspis capensis (Peters) :
CG 1587. Zygaspis quadrif rons (Thominot) : CG 1824, 1826.
Trogonophidae. — Agamodon a. anguliceps Peters: CG 361­20, 361­29. A. compressus
Mocquard: CG 3330, 10149. Diplometopon zarudnyi Nikolski : CG 1688. Pachycalamus
brevis Günther: CG 2511, 2512. Trogonophis wiegmanni elegans (Gervais): CG 1897,
1899.
190
ZOOLOGISCHE MEDEDELINGEN 41 (1966)
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VANZOLINI,