OCT., 1915. MAMMALS FROM BRAZIL AND PERU OSGOOD. 189 



continuous across parietals to outer edges of interparietal; f rentals 

 somewhat expanded behind; anterior border of interparietal somewhat 

 concave; palatine foramina large; mesopterygoid fossa extended for- 

 ward at least to plane of last molars. 



Measurements: Three adults, measured by the collector: Total 

 length, 389, 375, 374; head and body, 201, 193, 194; tail 188, 182, 180; 

 hind foot with claw 45, 45, 42. Skull of type: Greatest length 41.2; 

 basilar length 32.5; mastoid breadth 15.2; nasals 16.3x4.8; interorbital 

 breadth 4.8; length of fronto-parietal suture (between ridges) 8.1; 

 interparietal 10.8x3; palatine foramina 8.7x3; diastema 12.5; upper 

 toothrow 7.4. 



Remarks: The water rats of the genus Holochilus heretofore have 

 been known only from extreme eastern South America, but the taking 

 of an immature specimen in Eastern Peru * and the discovery of the 

 above described form in the middle Amazon region indicates that their 

 range is much more extensive. Of the described forms, only H . guianae, 

 H. sciureus, and H. nanus are geographically near the one here named. 

 H. nanus of the lower Amazon region is so much smaller that it need 

 not be considered. H. sciureus (type locality, San Francisco River, 

 Brazil) evidently is closely related but its skull, as figured by Winge, 

 is so much smaller, that there is no doubt of its distinctness. H. 

 guianae, from the Kanuku Mts., is described as having the interorbital 

 region flat without elevated ridges, a character not shown by our 

 species. The remaining species of the genus inhabit southeastern 

 Brazil and Argentine and on account of their heavier dentition are well 

 distinguished from the northern forms. Doubtless all the species are 

 very similar in color. 



Phyllotis definitus sp. nov. 



Type from Macate, 50 miles northeast of Chimbote, Peru. Altitude 

 9,000 ft. No. 21125 Field Museum of Natural History. Adult male. 

 Collected Feb. 14, 1914 by M. P. Anderson. 



Characters: A large full-pelaged species of relatively deep rich color 

 and with the tail about equalling the head and body in length. Upper 

 parts cinnamon brown mixed liberally with dusky, the rump slightly 

 lighter than the back and the shoulders and nape inclining to grayish; 

 nose, forehead, and sides of face decidedly grayish in definite contrast 

 to the body; inside of ears nearly clear ochraceous, outside with some 

 mixture of dusky; under parts buffy ochraceous, paler and more whitish 



* See Field Mus. Nat. Hist., Pub. 176, Zool., X, p. 167, Apr. 20, 1914. 



