mark on anterior part of
each prefrontal and another on interparietal seam; an indistinct
pale gray crescent on posterior border of nostril; narrow cream band
covering posterior edges of parietal and half of first dorsal scale
row, widening laterally to include temporal and posterior two or
three supralabials; throat cream (except for dark markings on
mental, on first three infralabials, and on anterior chin shields),
its pale area continuous with pale band on head; body and tail
marked with alternating white and black rings; white rings
(excluding band on head) 38 on body, 17 on tail; each white ring
alternately one and two scales wide dorsally (producing wavy or
zigzag effect), widened laterally, and three to four scales wide on
belly; black rings three to four and one half scales wide on
middorsal line, and two to three scales wide on belly; black and
white rings (excepting first black ring behind head) continuous
around body and tail. Colors described above nearly same as in
living specimens.

_Range._--The species is known only from three localities on the
Pacific drainage of southwestern Chihuahua; the geographic range
probably includes parts of southern Sonora and northern Sinaloa. The
discovery of _Geophis_ in southern Chihuahua increases to 21 the
number of species of the genus known to occur in Mexico and extends
the known range of the genus approximately 560 miles northwestward
from the type locality of _G. latifrontalis_, a point 50 miles south
(in Guanajuato?) of San Luis Potosi, or, a slightly lesser number of
miles north-northwestward from an indefinite locality for _G.
bicolor_ in western Jalisco (La Cumbre de los Arrastrados)
(Boulenger, Catalogue of the snakes in the British Museum, Vol. 2,
1894, p. 298).

_Variation._--Standard counts of scales are given for the paratypes
as well as the holotype in table 1. The fifth and sixth supralabial
scales are fused on both sides of one specimen (UMMZ 117771) as is
the case on the left side of the holotype. Except for one specimen
(UMMZ 117770) that has a small anterior temporal separating the
posterior two-thirds of the fifth supralabial from the parietal on
each side, the temporal formula in the type series is uniformly 0 +
1.

TABLE 1.--COUNTS OF SCALES, MEASUREMENTS, AND OTHER DATA
PERTAINING TO HOLOTYPE AND PARA