1893.] Allen on Mammals from Costa Rica. 239 



14. Sitomys nudipes Allen. 



Hesperomys ( Vcsperitmis) nudipes ALLEN, Bull. Am. Mus. Nat. Hist. Ill, p. 

 213, April 17, 1891. 



Two specimens, Santa Clara, A. Alfaro. Both are immature 

 and differ from the type (see this Bulletin, 1. c.) in being much 

 darker, especially above, as would be expected in the young. 

 Above the pelage is black with a faint tinge of sooty brown, 

 passing into grayish black on the sides, and then into the purer 

 gray of the ventral surface, which is tinged more or less with 

 yellowish rusty over the pectoral region. The ears and tail are 

 naked, and the abruptly whitish feet are thinly haired. 



An adult skin and skull, from near San Jose, collected and 

 presented to the Museum by Mr. George K. Cherrie since the 

 publication of the original description, agrees with the type. 



This is an aberrant Sitomys, but the species seems to belong 

 here rather than elsewhere. 



*I5. Oryzomys costaricensis, sp. nov. 



Size very small ; ears small ; tail one and a half times the length of the head 

 and body. Pelage full, long (7 mm. on middle of back), soft, but rather coarse 

 for so small a mouse. 



Above yellowish brown, varying to yellowish chestnut, with a heavy admix- 

 ture of black hairs ; sides paler, ochraceous buff with little or no black, passing 

 gradually into the clear, rather strong buff of the ventral surface, which is sepa- 

 rated from the color of the upper parts by a quite distinct but narrow fulvous 

 lateral line. Ears small (height above crown, in dried skin, about 7 mm.), 

 oval, well haired on both surfaces, dusky brown externally, darkest on the 

 anterior third, more yellowish on the inner surface. Upper surface of fore and 

 hind feet buffy white, scantily haired, especially the hind feet, where the short 

 light-colored hairs scarcely conceal the scaly annulations ; palms and soles 

 naked, flesh-colored, the latter 6-tuberculate. Tail very long, naked, unicolor, 

 'pale brown. 



Total length, 196 mm. ; head and body, 79 ; tail, 117 ; hind foot, 23 (aver- 

 age of three specimens, from measurements made before skinning) ; ear from 

 crown, 7 (from skins). 



The skull is that of a nearly typical species of Oryzomys in all of its essen- 

 tial features, except that the supraorbital ridge is so feebly developed as to be 

 quite lacking, even in a skull with well-worn teeth. An adult skull measures as 

 follows : Total length, 21 mm. ; basal length, 17.8 ; greatest zygomatic 

 breadth, 11.4 ; greatest breadth of brain case, 10.1 ; least interorbital breadth, 



