imens, Milstead concluded that _T. cyrtopsis
postremus_ was not subspecifically distinct from _T. cyrtopsis
cyclides_. Recently, Fitch and Milstead (1961) showed that _Thamnophis
dorsalis_ Baird and Girard (1853) was the correct name for the snakes
that had been recognized as _Thamnophis cyrtopsis_ Kennicott (1860).
Consequently, the snakes referred to _T. eques eques_ by Smith (1942)
and to _T. cyrtopsis cyclides_ by Smith (1951) and Milstead (1953) are
now _T. dorsalis cyclides_.

Aside from one specimen from Temazcal and nine from Morelia (paratypes
of _T. vicinus_), only two other specimens completely lacking the
middorsal stripe have been seen; one is a male (UMMZ 102510) having 161
ventrals and an incomplete tail from Pino Gordo, and the other is a male
(CNHM 39060) from Tancitaro having 158 ventrals and an incomplete tail.
A female from Tancitaro (CNHM 39061) having 153 ventrals and 77 caudals
has no lateral stripes and only a narrow middorsal stripe on the
anterior part of the body. Throughout the region where _T. vicinus_-like
snakes have been found, typical _T. dorsalis cyclides_ occurs in much
greater numbers. I concur with Bogert and Oliver in placing _T. vicinus_
as a synonym of _T. dorsalis cyclides_.

[Illustration: FIG. 10. Dorsal color pattern of _Thamnophis dorsalis
cyclides_ (A) and _Thamnophis dorsalis postremus_ (B).]

Milstead (1953) had available few specimens of _Thamnophis dorsalis_
from the Tepalcatepec Valley. The large series now in existence shows
that the population in the Tepalcatepec Valley differs distinctly from
that inhabiting the Mexican Plateau, Cordillera Volcanica, and Sierra de
Coalcoman. Therefore the name _T. dorsalis postremus_ Smith (1942) is
resurrected for the population in the Tepalcatepec Valley. _T. dorsalis
cyclides_ and _T. dorsalis postremus_ differ in color pattern (Fig. 10)
and in scutellation (Table 6). Specimens from the Mexican Plateau and
mountain ranges have a distinct light stripe on the second and third
scale rows, a dark brown dorsum having squarish black spots, and a row
of dark spots on the first row of dorsal scales. Specimens from the
Tepalcatepec Valley have a grayish brown dorsum having smaller and less
distinct dark spots and no light stripe on the second and third scale
rows; the first, second, and third rows of scales are colored like the
venter. In some specimens there are small dark flecks on the first row
of dorsal scales.

TABLE 6.--VARIATI