Vol. 32, pp. 213-216 December 31, 1919
PROCEEDINGS
OF THE
BIOLOGICAL SOCIETY OF WASHINGTON
TWO NEW CROTALINE SNAKES FROM WESTERN
MEXICO.
BY E. R. DUNN.
Among the many reptiles brought back from Mexico by
Nelson and Goldman were three small snakes, two rattlers and
a Lachesis. The two rattlesnakes are obviously alike and appear
to be unnamed. So likewise the Lachesis seems to be hitherto
unknown.
In naming these new snakes after Dr. Stejneger and Dr. Bar-
bour. I gladly take advantage of an opportunity to show my
appreciation of the advice and encouragement which they have
so often given me.
Lachesis barbouri, sp. nov.
Diagnosis.—A small Lachesis with single subcaudals, 17 rows of scales,
and an enlarged f— ronta 1 shield.Range.— Omilteme, Guerrero, Mexico.
Type. United States National Museum, No. 46,347. Omilteme, Guer-
rero, Mexico. —
Description of type specimen. Scales in 17 rows, the first smooth, the rest
keeled. Ventrals 154, anal entire, subcaudals 32 (23 single, followed by
three paired shields followed again by six single ones) . Tail apparently not
prehensile. Supraoculars large, separated across the head by three shields
of which the median is a large frontal and the lateral ones form part of a row
separating frontal from —supraocular. Supralabials eight left, nine right
none entering pit. Infralabials nine, three touching the one pair of geneials.
Two preoculars, four suboculars, two of which touch the third and fourth
—labials and the last two of which are separated by one scale
from the labials
three postoculars. There are from one to three keels on the temporal
scales. Nasal divided—one scale between preocular and nasal, a large
scale in front of supraocular on top of snout. Canthus rostralis while dis-
tinct does not form an acute ridge as in L. godmani.
Uniform dull olive above. On the posterior fifth of the body there are
indistinct light spots on the ends of the ventrals and on some of the scales
44—Pboc. Biol. Soc. Wash., Vol. 32, 1919. (213)
214 Proceedings of the Biological Society of Washington.
of the first three rows. These take the form of light bars four or five dorsal
scale lengths apart. The scale which has the light spot also has a dark tip.
On the tail these narrow cross bars extend to the mid-dorsal line. There
are four such light bars on the tail, the posterior third of which is uniform
and darker than the color elsewhere. The belly is very finely punctulated
with light and dark. Head above same as body, an indistinct light band
from eye to angle of jaw including the last four upper labials and extending
more or less continuously though faintly above the edges of the ventrals
through the anterior half of the body. Throat dark, last six lower labials
with a vertical white bar.
Dimensions.—— Length, 370 mm. ; tail, 46 mm.Remarks. This snake merits comparison with L. godmani and L. aurifer
rather than with any Lachesis hitherto recorded from Mexico (i. e., lanceo-
latus, nummifer, lansbergii, brachystoma and undulatus) . It has a lower scale
count than any American species.
With aurifer (the next lowest, with 19 scale rows) it is allied by the en-
larged frontal and the ventral count. But it differs in the smaller number
of subcaudals, in the two less scale rows, in the greater number of oculars,
and in some being in contact with the labials, in the divided nasal, in the
labials being occluded from the pit, and in coloration.
With godmani there is close agreement in coloration save in the peculiar
throat of the new form, the subcaudal count is the same. Godmani some-
times has the enlarged frontal separated by one row of scales from the
supraocular, the labials do not enter the pit, and the nasal is divided. But
here the resemblance ends for godmani has 21 scale rows, a much lower ven-
tral count, a more acute canthus rostralis and the suboculars are cut off
from the labials.
It would seem that barbouri is a link between godmani and aurifer showing
characters of both and being more primitive than either in head scalation
and having (dwarfing due to altitude?) a lower number of dorsal scale rows
than either.
It is interesting to note that godmani and aurifer are usually put in differ-
ent sections of the genus because of the possession of a prehensile tail by
aurifer, and these sections have been elevated at times to generic rank.
Bothriechis Peters 1859, type B. nigroviridis Peters, for the arboreal, pre-
hensile tailed forms; and Bothriopsis Peters 1861, type B. quadriscutatus
Peters (=castelnaudi D &B fide Boulenger etCope), for the terrestrial, non-
prehensile tailed forms.
I do not believe that these divisions can be maintained on this character.
Bothriechis is therefore the generic name for the American Lachesis with
undivided subcaudals in case they are thought not congeneric with L. mutus
and L. atrox.
Crotalus stejnegeri, sp. nov.
Diagnosis.—A small Crotalus with a long slender tail, a very small rattle
and with the first pair of lower labials long and produced backwards broadly
in contact behind the symphysial.
Dunn—Two New Crotaline Snakes from Western Mexico. 215
Range.—West coast of Mexico in Sinaloa and western— Durango.
Type. United States National Museum, No. 46,486. Plumosas, Sinaloa,
Mexico; July 19, 1897. Nelso—n and Goldman collectors.
Description of type specimen. Scales in 27 rows, the first smooth, the rest
keeled. Ventrals 176, anal entire, caudals 44 undivided. Rattle very
small, seven rings and button measuring 12 mm. long and four mm. wide.
Upper surface of snout with one large pair of internasals and a row of four
prefrontals, the two outside ones in contact with internasal and— surpraocularcanthus rostralis d—istinct. Supraocular shields narrower than space be-tween them, smooth 7-9 scales between supraoculars, and 10-13 scales in
contact with them. Two scales between eye and nasal. Eye separated
from labials by three series of scales. Rostral in contact with nasal. Supra-
labials 14 L, 15 R; lower labials 16, the first pair produced backwards
in contact with each other behind the symphysial and with the third lower
labial, thus cutting the second lower labial from the chin shields. Color
grayish-brown; a series of 40 darker brown, black-edged dorsal rhombs (the
first of which is split on the neck) three scales long and on seven scale rows.
Alternating with these on the ninth scale row a dark spot covering about
one scale. In the same transverse plane as the dorsal rhombs dark spots
covering about one scale in each of the third, fourth and fifth rows. Alter-
nating with these a dark spot on a scale of the first row and the tip of the
preceding gastrostege. Belly grayish marbled with black. Tail dull brown
with indistinct dark cross-bands. Head flecked above with black, a darker
brown blackedged band from beneath eye to angle of jaw. Lower half of
upper labials white. Throat white, a dark spot below angle of jaw and tip
of lower jaw grayish.
Variation.—A smaller specimen with a rattle consisting of button alone—
United States National Museum, No. 46,460, with the same data, shows
few minor variations. On one side four series of scales separate eye from
labials. The second lower labial is narrowly in contact with the chin shield,
thus separating the first labial from the third. The scale counts for this
specimen are V 174, C 41, Sc 27, L 14/13-14. Same pattern as type.
Forty-four dorsal rhombs, two elongated black spots on occiput, a dark spot
which is partly on the posterior end of the supraocular and a similar spot
partly on the anterior end of the same scale.
Dimensions.—Type No. 46,486. Total length, 590 mm.; tail except
rattle 77 mm—. No. 46,460, total length, 284 mm., tail except rattle, 33 mm.Remarks. This snake scarcely needs comparison with any described
form. The subcaudals are more in number than in any of the described
species. The shape of the tail and the minuteness of the rattle are charac-
ters which scarcely stand out on paper but which are very striking in the
specimens. The peculiar shape of the first lower labial is unique, also.
In pattern stejnegeri is remotely similar to the snakes of the triseriatus-
pricei group, but even here the relationship is not close.
Boulenger (Cat. Snakes British Museum III, p. 580) records a specimen
of C. tigris from Ventanas, Durango, Mexico, on the western slope of the
Sierra Madre about 15 miles from the Sinaloa border and undoubtedly in
216 Proceedings of the Biological Society of Washington.
the same faunal zone as Plumosas. This snake was Boulenger's only speci-
men of tigris. It was small (380 mm.) and has the following scale count:
V 181, C 46, Sc 25. I strongly suspect that it is the present species. The
caudal count is far too high for tigris. Unfortunately it is impossible to
determine how much of the description in the Catalogue of Snakes is drawn
from this specimen and how much from literature. Still a comparison with
the description above shows many points of resemblance and a few of dis-
cord other than the two less scale rows and the slight ventral and caudal vari-
ations. Also the following statements are not in accord with the state of
" " "
affairs in tigris. Snout with distinct canthus, a large scale on each side
between the internasal and the supraocular," "three series of scales between
the eyes and the labials," "dark-edged spots."