NEW MAMMALS FROM MEXICO 561 



nasals decidedly more slender (nasals narrowly wedge-shaped, trun- 

 cate posteriorly on plane of premaxillaa) ; zygomata weaker and less 

 broadly spreading (probably due to immaturity) ; interparietal large, 

 broadly and strongly convex anteriorly, tapering to point on sides ; 

 incisive foramina broadest posteriorly and ending on plane of front of 

 molars; bulL-e slightly larger ; upper incisors weaker and more slen- 

 der ; molar series very large and heavy, decidedly larger and longer 

 than in midicatidus (measuring 9.5 mm.). 



Meastiretnents. — Type specimen ( $ yg-ad., probably not full 

 grown) : total length 448 mm. ; tail vertebrae 234; hind foot 46. 



TYLOMYS BULLARIS sp. nov. 



Type from Tuxtla, Chiapas, Mexico. No. 7605S. $ im. U. S. 



National Museum, Biological Survey Coll. Sept. 7, 1895. E. W. 



Nelson and E. A. Goldman. Orig. no. 8406. 



Characters. — Type and only specimen too young to give reliable 

 external characters. Ears very large, black, and sparsely haired; tail 

 long and slender, naked, basal third blackish, terminal two- thirds yel- 

 low. Color paler and grayer than young of corresponding age of 

 nudicaudtis ; underparts white ; upper lip and patch on side of nose 

 whitish ; face much paler than in nudicatidus ; fore feet brown to base 

 of toes; toes and edging on outer side of foot white; hind feet to toes 

 dark brown ; toes white. 



Cranial characters. — Skull similar to that of nudicaudiis of cor- 

 responding age, but interparietal broader on outer side; zygomata 

 more strongly spreading posteriorly; bullce widely different, large and 

 broadly rounded anteriorly, without anterior prolongation, suggesting 

 the condition in Ototylomys. Teeth of same size as in midicaudiis. 



Remarks. — I am reluctant to describe a new mammal from an 

 immature specimen, but in this instance no other course seems open. 

 The white upper lip and patch on side of nose, the pale grayish 

 plumbeous of the upperparts, and the peculiar character of the audital 

 bullae seem to distinguish the species from its congeners. It is hoped 

 that adults will be obtained in the near future. 



Measurements. — Type specimen ( $ im., not nearly full grown) : 

 total length 324 mm. ; tail 158; hind foot 37.5. 



OTOTYLOMYS gen. nov. 



Exter7ial characters. — Appearance rat-like; ears large, thin and 

 naked; tail long and naked. 



Cranial characters. — Skull flattened, with large interparietal and 

 strongly developed superciliary ridges which form a horizontal shelf 



