Bulletin American Museum of Natural History. [Vol. XXIV, 



The type is a very old male. Three other specimens, the smallest a young adult, 

 measure respectively as follows: total length, 280, 310, 340; tail, 150, 170, 180. 



The skull, particularly in the old specimens, is very broad and heavy, with the 

 supraorbital ridge very heavy and broadly overhanging the orbits. Total length 

 (type), 36; condylo-basal length, 30; zygomatic breadth, 20; interorbital breadth, 

 7; mastoid breadth, 13; length of nasals, 14; upper toothrow, 6. Posterior border 

 of nasals ending in a V-shaped point, opposite the front border of the orbit. Anterior 

 palatal foramina short and broad, 5X2 mm. The skull in 4 specimens (one a 

 young adult) averages, total length, 35.5; zygomatic breadth, 19. 



0. ochraceus differs greatly from any other species of Oryzomys known 

 to me. A marked feature is its heavy soft pelage, which has a length on 

 the back of about 15 mm., the basal four-fifths of which is deep plumbeous, 

 the hairs individually tipped with rufous, mixed with others tipped with 

 black. On the ventral surface the basal part of the pelage is grayish plum- 

 beous, the surface heavily washed with deep buff or pale yellow. In external 

 measurements it is much smaller than 0. devius Bangs, from Chiriqui, 

 and differs from it markedly in coloration, in the character of the pelage, 

 and in the form of the skull (compared with topotypes of 0. devius). 

 From 0. talamancai Allen (compared with the type) it differs in much 

 larger size and in coloration. It also appears quite distinct from any 

 species thus far known from Guatemala or Mexico. 



[I take the present opportunity to describe a strongly marked new spe- 

 cies of Oryzomys from Costa Rica, collected by M. A. Carriker, Jr., in 

 1904, as follows: 



Oryzomys carrikeri sp. nov. 



Type, No. 25976, $ ad., Rio Sicsola, Talamanca, Costa Rica, August 18, 1904; 

 M. A. Carriker, Jr., for whom the species is named. 



Pelage very short, fine, soft and velvety. Sides, from nose to rump, ochraceous 

 brown; back dark brown suffused with ochraceous; below, from chest to base of 

 tail, uniform gray dark gray in worn pelage, gray washed with whitish in fresh 

 pelage ; chest and throat whitish nearly white in fresh pelage ; ears of medium 

 size, dark brown, almost naked; fore feet whitish, hind feet flesh color, nearly 

 naked; tail practically naked (all the scales distinctly visible), dull brown above, 

 lighter below, especially on the basal fourth. 



Total length (type), 265 mm.; tail, 133; hind foot, 30.5 (collector's measure- 

 ments). Two other specimens measure respectively: (J 1 ad., 248, 121, 29.5; $ 

 juv. ad. (a nursing female), 240, 118, 30. Skull (type), total length, 31.5; condylo- 

 basal, 26; zygomatic breadth, 14.7; interorbital, 5; mastoid, 11.2; nasals, 12; upper 

 molariform series, 5. The adult male skull gives essentially the same measure- 

 ments; the young adult female skull is about 2 mm. shorter, with the other dimen- 

 sions in proportion. The nasals extend posteriorly considerably beyond the pre- 

 maxillaries and end in an obtusely V-shaped point. The supraorbital ridges are 

 well-developed; the anterior palatine foramina are narrow anteriorly and diverge 

 posteriorly, the two foramina forming a V-shaped opening. 



