heeler's Rept.
Geog. Geol. Expl. Surv. W. 100th. Mer., vol. 5, p. 533,
1875.

Tacicuaro (4); Tupataro (2).

Formerly this species was abundant in the marshes around Lago de
Chapala. The draining of these marshes probably resulted in reducing the
numbers of these rattlesnakes. The species is known only from the
Mexican Plateau at elevations of 1450 to 2400 meters.

~Crotalus pusillus~ Klauber

_Crotalus pusillus_ Klauber, Bull. Zool. Soc. San Diego,
26:34, August 8, 1952.--Tancitaro, Michoacan, Mexico.

Acuaro de las Lleguas (2); Carapan; Cerro Tancitaro (16);
Dos Aguas (12).

Aside from the type series of _Crotalus pusillus_ from Cerro Tancitaro
and one specimen from Carapan referred to the species by Klauber
(1952:38), there are fourteen specimens from the Sierra de Coalcoman.
These specimens (UMMZ 112566-7, 118591-9, 118601, 121512-3) are like
_Crotalus pusillus_ from Cerro Tancitaro in having the prefrontals
paired, a black proximal rattle, and the underside of the tail black.
The prefrontals are bordered posteriorly by one scale in two specimens,
by two scales in three specimens, and by three scales in the other nine.
The snakes from the Sierra de Coalcoman have 40 to 46 (42) dorsal body
blotches. Ten males have 150-158 (154.4) ventrals and 29-33 (31.0)
caudals; two females have 157 and 160 ventrals, and 25 and 27 caudals.
The largest specimen is a male having a body length of 545 mm. and a
tail length of 63 mm. The only noticeable difference between the
specimens from the Sierra de Coalcoman and the topotypic series is that
the latter have fewer dorsal blotches; the range of variation is 33 to
46 (39.8).

Most specimens of this species have a grayish brown dorsum and dark
brown dorsal blotches. Two specimens from Dos Aguas (UMMZ 118596 and
118599) are pale brown above and have indistinct blotches.

One specimen from Dos Aguas regurgitated a large _Gerrhonotus imbricatus
imbricatus_; of two others from the same locality, one regurgitated a
_Sceloporus bulleri_ and an _Eptesicus fuscus_. The latter specimen was
collected at the entrance of a small cave, where it probably had
captured the bat.

In the Cordillera Volcanica _Crotalus pusillus_ has been obtained in
pine-oak forest at elevations between 1550 and 1800 meters. In the
Sierra de Coalcoman two specimens were taken in pine forest at an
elevation of 2300 meters; ten other were found beneath rocks and logs in
pine