266 



General 



large 



[1894. 

 ; color 



Fig. 5. P. moxi 

 ciuns. 



PKOCEEDINGS OF THE ACADEMY OF 



characters. — Size small; raastoifl bulla? 

 fuliginous in winter pelage. 



Color. — Winter pelage : Upper parts fuliginous or 

 dusky ; under parts and feet white ; a rather large 

 patch behind each ear, and a broad lateral stripe 

 (reaching from side of face to hind legs) ochraceous; 

 tail indistinctly bicolor, pale dusky above, whitish be- 

 neath. Summer pelage: Upper parts ochraceous, ob- 

 scured by the profuse admixture of black-tij)ped hairs. 

 Cranial characters. — Skull as in P. jiavm, but 

 audital bulla? separated anteriorly by breadth of 

 basisphenoid. 

 Perognathus (Cheetodipus) nelsoni sp. uuv. (Fi^. <j). 



Type from Hacienda La Parada, San Luis Potosi, Mexico. 

 No. 50,214, 9 , old, U. S. Nat. Museum, Department of Agri- 

 culture Collection. Collected August 19, 1892, by E. \\. Nelson. 

 (Original number 3, 207. ) 



Measurements (taken in tlesh). — Tz/pe; Total length, 190 mm; 

 tail vertebrae, 105; hind foot, 24. Ear from anterior base, 8 (in dry 

 skin). Average measurements of 14 specimens from type loealitv : 

 Total length, 178; tail vertebne, 101; hind foot, 23. 



General characters.— ^\ZQ rather small; ears rather long; tail of 

 medium length and moderately crested on distal 

 half; pelage rather coarse, with a few slender 

 spines on the rump (the spines are absent in the 

 young and in certain conditions of the molt). 

 Apparently C. nelsoni is an offshoot from the 

 intermedins- ohscniras type, from which it differs 

 widely in external appearance and less markedly 

 in cranial characters. 



Color. — Summer pelage coarse : Upper jDarts 

 grizzled yellowish-brown from admixture of coarse 

 huffy' and black hairs. Winter pelage finer, and 

 grayish black in color. Under parts and feet 

 white; tail bicolor, white below, brownish- dusky above, becoming 

 blackish distally. 



Cranial characters. — Skidl similar to that of intermedins, but 

 somewhat larger; maxillary arms of zygomata more squarely spread- 

 ing; nasals decidedly larger and longer. 



Fig. (>. I 



