NATURAL SCIENCES OF PHILADELPHIA. 281 



tips. The whole under surface, together with the feet, roost of the 

 fore leg and the inner aspect of the hind leg, is white, and on these 

 white areas the hairs are of this color to the roots. The line of 

 demarcation with the fawn color is pretty sharp, but less so in 

 some cases than in others, sometimes the whole belly showing a 

 tawny shade. The tail is bicolor; a brown or dusky stripe runs 

 the whole length of the upper surface ; the sides and under surface 

 being white or tinged with rusty; the latter particularly when the 

 white of the belly is similarly tinged. Besides these special mark- 

 ings, there is decided indication of a dusky stripe from the nose 

 under the eye and ear to the side of the neck, produced by increase 

 of the blackened tips of the hairs along the line. Some of the 

 whiskers are black, others being colorless. The pouches are white 

 inside. The claws are colorless. 



The series of specimens at mj 7 command does not suffice for a 

 complete exposition of the variation in color of this species. In 

 all the lateral stripe is conspicuous, and the other characters differ 

 little. I note, however, a decidedly richer tone in the Mexican 

 and Texan specimens than in those from Kansas and Nebraska. 



It is probable that the skull of this animal, when examined, will 

 afford some appreciable specific characters, in size at least, if not 

 in details of conformation. 



Perognathus penicillatus, Woodh. 



Perognathus penecillatus, Woodh., Proc. Acad. Nat. Sci. Phila. vi. 1853, 



200. (San Francisco Mts., Arizona.) 

 Perognathus 'penicillatus, Woodh., Sitgreaves' Rep. Expl. Zuni and Col. R. 



1853, 49, pi. 3. Le C, Proc. Acad. Nat. Sci. Phila. 1853, 225. 



(Mere mention.) And. and Bach., Q. N. A. iii. 1854, 298. (Copied 



from Woodh.) Bd., M. N A. 1857, 418, pi. 20, f. 5. Gray, P. Z. 



S. 1868, 201. (Wrong locality assigned. 1 ) Coues, Am. Nat. i. 1867. 

 Perognathus parvus, Le Conte, Proc. Acad. Nat. Sci. Phila. vi. 1853, 225, 



in part. Not Gricetodipus parvus, Peale. (The specimen noticed, 



from the Colorado Desert, is apparently a very young example of P. 



penicillatus. ) 



Diagn. About the size of Hesperomys leucopus. Tail vertebras 

 obviously longer than head and body. Hind foot more than one- 

 fourth the length of head and body. Tail crested above towards 



1 The San Francisco Mountains are several hundred miles from San Fran- 

 cisco City, California, nearly in the middle of Arizona formerly a part of 

 New Mexico. The locality appears to puzzle some writers. 



