1893-] Allen and Chapman on Trinidad Mammals. 215 



the former flesh-colored, the latter dusky brown, 6-tuberculate. Tail consider- 

 ably shorter than head and body, naked, very distinctly and clearly annulated 

 in comparison with the two preceding species. 



Measurements, from fresh specimens : Total length, 252 mm. ; head and 

 body, 135 ; tail, 118 ; hind foot, 28 ; ear from crown, 18. 



Young. Pelage very short, soft and velvety, almost plush-like on the ven- 

 tral surface. Above blackish plumbeous, paler on the sides, whitish gray 

 below. Later the back becomes nearly black, and the sides acquire a mouse- 

 brown wash. 



The skull is of the typical Oryzomys style, with, however, the facial portion 

 somewhat lengthened, and the anterior palatine foramen rather short and broad, 

 and the supraorbital ridge, even in old individuals, rather feebly developed. 

 Total length 33 mm. ; basal length, 27; greatest zygomatic breadth, 17; greatest 

 mastoid breadth, 12.2; least interorbital breadth, 5; length of nasals, 12.7; 

 antero-posterior breadth of interparietal, 3.8 ; transverse breadth of same, 10.2 ; 

 distance between incisors and first molar, 7 ; length of crown surface of upper 

 molar series, 4.5 ; length of lower jaw, 20.3 ; height at coronoid process, 8.6. 



Type, No. ff, $ ad., Princestown, Trinidad, April 16, 1893, coll. Frank 

 M . Chapman. 



This species is based on a series of ten specimens, three of 

 which are fully adult, two nearly adult, and five in the blackish 

 plumbeous pelage of the young, varying in age from sucklings 

 to half or two-thirds grown. 



The peculiar blackish plumbeous pelage of the young recalls 

 the corresponding ' blue ' stage in the genera Sitomys, Neotoma 

 and Nectomys, but which is not found in the typical species of 

 Oryzomys, as the genus is represented in the United States. In 

 this species there is a slight deviation toward Sitomys in the rela- 

 tively slightly narrowed and lengthened facial portion of the 

 skull. The auditory bullae, however, are unusually small, even 

 for an Oryzomys, in which genus they are always much smaller 

 than in Sitomys. 



This species was not found associated with the other species of 

 Oryzomys, but was met with in the forests, where it seemed to 

 live beneath the roots of trees or stumps. 



16. Oryzomys brevicauda, sp. nov. 



Adult. Pelage full, soft, and long (9.5 mm. long on middle of back). Gen- 

 eral color above yellowish brown, darker and strongly varied with black-tipped 



