A New Snake of the Genus Geophis From Chihuahua, Mexico

by John M. Legler

Holotype.—Adult female, KU 44265, alcoholic; 23 mi. S and 1½ mi. E Creel, Chihuahua, Mexico; 23 July 1957; original number 198, Ronald H. Pine.

Paratypes.—(Total of five alcoholic specimens, all from Chihuahua) Male (probably subadult), KU 44266, same data as holotype; male, UMMZ 117770, Mojarachic, 23 July 1957, Irving W. Knobloch; females, UMMZ 111501-2, Maguarachic, August 1954, and UMMZ 117771, Maguarachic, August 1957, Irving W. Knobloch.

Diagnosis.—Size small; 15 rows of smooth scales; a high number of ventral (173 to 183) and subcaudal (55 to 64) scales; alternating dark and pale rings on body and tail; dark rings, and often pale rings, complete.

Description of Holotype.—Snout-vent length 327 mm.; length of tail 93 mm.; anal scale entire; ventral scales 181 + anal; subcaudal scales 63 + tip; dorsal scales in 15 rows on all parts of body; six supralabials (fifth and sixth fused on left side), third and fourth entering orbit; fifth supralabial largest and in broad contact with parietal, posterior temporal, and postocular; six infralabials on each side, first pair in contact behind mental; enlarged chin shields in two pairs, anterior pair longer than posterior pair; anterior chin shields in contact for half their length with fourth infralabials; rostral nearly as high as broad; internasal and prefrontal scales paired and distinct; anterior and posterior segments of nasals distinct and nearly equal in size; loreal twice as long as high, in contact with eye; preocular lacking (represented by minute scale on left side); vertical diameter of eye equal to distance from lower rim of orbit to free edge of upper lip; temporal formula 0 + 1, the single temporal scale separating sixth supralabial and parietal; one postocular and one supraocular on each side; all scales perfectly smooth; no scale-pits evident; dentary bone bearing eight teeth; maxillary bone bearing seven teeth; posterior tooth longest, thinnest, and separated from other teeth by slight diastema (maxillary teeth in UMMZ 111502, 6/7, dentary teeth 8/8, no diastema in maxillary series).

Fig. 1. Geophis aquilonaris new species, KU 44265, Holotype; lateral, dorsal, and ventral views of head and neck (approximately × 6).

Fig. 2. Geophis aquilonaris new species, KU 44265, Holotype; scalation and coloration at mid-body showing 19th and 20th white rings (approximately × 7).

Head slate-black above, having dim pale 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 Potosí, 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).