Bailey — North American Species of Sigmodon. 113 



Skull. — Similar to that of herlandieri but with narrower braincase, 

 double convex outlines of interparietal, smaller molars, and smaller, 

 shorter, more rounded bullae. 



Measurements. — Average of 8 adults from type locality: total length 

 244; tail 112; hind foot 31.6. Skull of type: basal length 29.3; nasals 

 13; zygomatic breadth 19.3; mastoid breadth 13; alveolar length of 

 upper molar series 6.4. 



Distribution. — Western Jalisco and southern Tepic in Western Mexico. 



Specimens examined. — San Sebastian, Jalisco, 10, San Bias 1, Tepic 2, 

 and Valle de Banderas 1. 



Remarks. — Although belonging to the Mspidus group, alleni is quite 

 distinct from all neighboring species, occurring at the type locality with 

 mascotensis, the west coast form of herlandieri, and at San Bias with 

 major. It is the species Dr. Allen had in mind in writing his description 

 of mascotensis from which he intended to separate the Colima form, but 

 as his two specimens of the species here named alleni were not fully 

 adult he unfortunately selected as his type another specimen that proves 

 to be the same as the form to which on the following page he gave the 

 name of colimae. As these two names apply to the same species I have 

 placed colimae as a synonym under mascotensis and taken the opportunity 

 of associating Dr. Allen's name with the species which he intended to 

 describe. 



Sigmodon fulviventer Allen. 



Sigmodon fulviventer Allen, Bull. Am. Mus. Nat. Hist., II, p. 180, 

 October 21, 1889. 



Type locality. — Zacatecas, Zacatecas, Mexico. 



General characters. — Size largest of the hairy tailed group; tail cov- 

 ered with short, bristly hairs that almost conceal the annulations; pe- 

 lage rather hispid. 



Color. — Upperparts yellowish brown, lightened on sides by white 

 bristles; upper half of outer surface of ear black; lowerparts and feet 

 clear rich fulvous ; tail brownish black above and below. 



Skull.— ^hort, wide, and heavily ridged, not much arched, not bulged 

 interorbitally; interparietal, about 2 mm. wide and not divided; supra- 

 occipital with a slight median ridge; nasals short, wide and rounded at 

 ends; jaw short and heavy with short, wide coronoid. 



Measurements.— "^yi^B: total length 270; tail 108; hind foot 33. Skull 

 of type: total length over incisors 35.5; nasals 13; zygomatic breadth 

 21.5; alveolar length of upper molar series 6.3. The broken base of the 

 skull makes the usual set of measurements impossible. 



Distribution. — Known only from two localities; from about 8000 feet 

 altitude near the city of Zacatecas and from Durango, Durango. Speci- 

 mens examined 2. 



