nd a
_torquata_-type (a somewhat narrower dark nape-band bordered anteriorly
by a pale nuchal area, and no dark nape stripe). Snakes having the
_ochrorhyncha_-type of nuchal pattern are found on the Mexican Plateau
from Michoacan northward into the desert regions of Sonora and the
southwestern United States. Snakes having the _torquata_-type of pattern
are found on the coastal lowlands and adjacent slopes of the Sierra
Madre Occidental from southern Sinaloa to Colima and thence inland in
the Balsas-Tepalcatepec Basin to Morelos and Guerrero. An exception is
_Hypsiglena torquata dunklei_ from Forlon and San Fernando, Tamaulipas;
it has the _torquata_-type of nuchal pattern. The distributional picture
is somewhat complicated because some individuals having the
_torquata_-type of nuchal pattern also have a faint nape stripe. If
these are taken as exceptions, the general picture of distribution in
Mexico is _H. t. torquata_ on the Pacific lowlands from Sinaloa
southward to the Balsas Basin and _H. t. ochrorhyncha_ on the Mexican
Plateau.

Smith (1943:433) resurrected _Hypsiglena jani_ Duges for the snakes of
the _ochrorhyncha_-type on the southern part of the Mexican Plateau. He
stated that the southern specimens differed from northern ones in having
a nuchal spot 9 or 10 scales in length, as compared with a spot 2 to 6
scales in length in northern specimens. A cursory examination of
specimens from the areas between Arizona and Michoacan showed that there
is a gradual increase in the size of the spot from north to south. If no
other characters can be found to distinguish the populations, they
should be considered as a single subspecies.

_Hypsiglena affinis_ differs from _H. torquata_ in possessing 19 instead
of 21 rows of dorsal scales. Additional material is needed from the
western slopes of Jalisco and the Barrancas in Zacatecas and Durango,
before definite allocation of _affinis_ can be made.

Bogert and Oliver (1945:379) discussed the status of certain named
populations in Baja California and concluded that only one species
occurs there, and that the species probably is conspecific with _H.
torquata_. A careful review of the genus _Hypsiglena_ might show that
there is only one species.

The one specimen from Michoacan (USNM 46513) is from an elevation of
about 2300 meters near the southern edge of the Mexican Plateau.

~Hypsiglena torquata torquata~ (Guenther)

_Leptodeira torquata_ Guenther, Ann. Mag. Na