POCKET MICE FROM LOWER CALIFORNIA. 



461 



that specimens from the middle part of the peninsula 

 (Comondu) are intermediate between it and spinatiis. 



Perognathus arenarius sp. nov. 



Type from San Jorge, near Comondu, Lower Califor- 

 nia. No. 99 ? ad. Collection of California Academy 

 of Sciences. Collected March 17, 1889, by Walter E. 

 Bryant. Original number, 242. 



Measurements (taken from well made dry skin). — 

 Type: Total length, 136; tail vertebras, 70; hind foot, 

 20; ear from anterior base, 7. 



General characters. — Size smallest of the known 

 species of Chcetodiftis; pelage hispid but not spiny; no 

 spines on rump or elsewhere; tail rather short and only 

 sparsely crested; skull broad and square. 



Color. — Upper parts drab-brown, darkest 

 along the middle of the back, and not notice- 

 ably mixed with black-tipped hairs; under 

 parts, fore legs and feet and hind feet white; 

 no lateral line; tail bicolor, brownish above, 

 white beneath. 



Cranial characters. — Skull short and broad ; 

 maxillary arms of zygoma standing out squarely 

 "'• and widely, so that the zygomata are parallel 

 instead of narrowing anteriorly; interparietal more than 

 twice as broad as long, strap-shaped or broadly and flatly 

 pentagonal, broadest in front; parieto-occipital suture 

 opposite antero-lateral corner of interparietal; audital 

 bulla? much swollen and rather short. Total length of 

 skull, 22.5; mastoid breadth, 12; zygomatic breadth an- 

 teriorly, II. 



General remarks. — P. arenarius is a member of the 

 ■penicillatus ^t.x\^^, and is the smallest species of the group 

 yet described. 



Fig 4. P, arc liar ius 



