-oak forest at an elevation of 2100 meters.

~Crotalus triseriatus aquilus~ Klauber

_Crotalus triseriatus aquilus_ Klauber, Bull. Zool. Soc. San
Diego, 26:24, August 8, 1952.--Alvarez, San Luis Potosi,
Mexico.

Morelia (10); Tacicuaro (2).

I am following Klauber (1952) in assigning some of the specimens of this
species from Michoacan to the subspecies _aquilus_ and others to _C. t.
triseriatus_. The distinguishing characters of these subspecies are
given by Klauber (1952:28). On the basis of the few localities from
which the species is known in Michoacan it seems as though _C. t.
aquilus_ inhabits the open grassy areas on the Mexican Plateau and the
associated open pine-oak or oak-bunch grass habitats to the north and
east of the Cordillera Volcanica. _Crotalus triseriatus aquilus_ has
been collected at elevations from 1600 to 2000 meters in Michoacan.

~Crotalus triseriatus triseriatus~ (Wagler)

_Uropsophus triseriatus_ Wagler, Natuerliches System der
Amphibien, p. 176, 1830.--Mexico. (Probably Mexico City.)

_Crotalus triseriatus triseriatus_, Klauber, Bull. Zool.
Soc. San Diego, 26:19, August 8, 1952.

Cerro Tancitaro (36); Opopeo; Patzcuaro.

This small rattlesnake inhabits rocky areas in pine and pine-oak forests
above 1600 meters in the Cordillera Volcanica; it has been collected at
3270 meters on Cerro Tancitaro. The series reported by Schmidt and
Shannon (1947:84) is a mixture of specimens of _Crotalus triseriatus_
and _Crotalus pusillus_. The two species are found together on Cerro
Tancitaro, but only _Crotalus pusillus_ inhabits the coniferous forests
of the Sierra de Coalcoman. Klauber (1952:30) stated that despite the
proximity of _Crotalus triseriatus triseriatus_ and _Crotalus
triseriatus aquilus_ in Michoacan, there is no evidence of
intergradation. He went on to suggest that additional material might
show that the two named populations actually are distinct species. The
specimens that have been studied since Klauber's investigations also
show no evidence of intergradation, but there still is no known sympatry
of the populations.

The small montane rattlesnakes belonging to the species _C. pricei_, _C.
pusillus_, and _C. triseriatus_ present a problem in systematics and
distribution worthy of intensive investigation. A knowledge of the
distribution and relationships of the various populations of these
snakes, together with other species also