98 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 



HESPEROMYS CALIFORNICUS, (Gambel) Baird. 

 Parasitic Mouse. 



llus caUfornicua, Gambel, Proc. Acad. Nat. Sci. Phila. iv, 1848, 78 (Monterey). 

 Besperornys californicus, Baird, M. N. A. 1857, 478 (Santa Clara County, Cal.). 

 Hesperomys ( Vesperimus) californicus, Coues, Proc. Acad. Nat. Sci. Phila. 1874, 180. 

 Besperomys parasiticus, Coofbr, MSS. — Baird, op. cit. 479 (in text). 



Diagnosis. — H. crassitie dimidium muris decumanus subcequans, caudd lon- 

 gissimd subnudd vix bicolore, pedibus uncialibus plantis nudis, auriculis maxi- 

 mis sparsissime pilosis; supra fuscus, lateribus sensim Jlavicantibus, Infra 

 a/bidus. 



Nearly as large as a half-grown house-rat, with extremely long nearly 

 naked ears and tail, the latter scarcely bicolor ; feet an inch long, with naked 

 soles; dark grayish-brown above, becoming pale cinnamon-brown on the 

 sides, the under parts whitish.' 



Habitat. — Southern and Lower California. 



Our few specimens, mostly the same as those described by Baird in 1857, 

 indicate a species perfectly distinct from leucopus. The animal looks, in fact, 

 much like a partly-grown Neotoma ; it is quite as large as some examples of 

 Oryzomys palustris, while its long and sparsely hairy tail, no less than its 

 size, gives it somewhat the aspect of a young Norway rat. No one of the 

 interminable variations of leucopus have so far shown us anything like this. 



The size and proportions of the species are illustrated in the table given 

 below. It may be said to be four or five inches in length of trunk, with 

 the tail about the same — half an inch longer or as much shorter than the 

 head and body. The feet are an inch or a little more long, and share witli 

 eremicus the peculiarity of naked soles, although the very extremity of the 

 heel is not perfectly denuded. The immense ears are a striking feature, 

 measuring three-fourths of an inch or more in height by about two-thirds of 

 an inch in width. They are very closely pilous on both sides, as will be seen 

 by close inspection, but appear at first sight quite naked. The little hairs are 

 so short that they do not form any perceptible fringe. The shape of the ear 

 is also remarkable; instead of being evenly rounded, it is like the two sides 

 of a rectangle with the upper corner rounded off. The tail is scant-haired, 

 showing the annuli plainly. 



The pelage is remarkable for its softness, fullness, and gloss, although it 

 is not long, measuring less than half an inch on the back. Tt is very different 



