1 88 FIELD MUSEUM OF NATURAL HISTORY ZOOLOGY, VOL. X. 



19. Skull of type: Greatest length 37.9; basal length 36.9; zygomatic 

 breadth 19; least interorbital breadth 6.2; nasals 7. 9 X 3.9; palate length 

 from gnathion 21.4; upper toothrow c to m 4 15.7; combined length 

 ms 1 ' 3 6.6. 



Remarks: The type locality of Marmosa impavida as given by 

 Tschudi is the forest region of eastern Peru between 10 and 12 latitude 

 south. A specimen lately received from this very region indicates that 

 typical impavida is appreciably different from the animal of northern 

 Peru. This specimen was collected by M. P. Anderson at San Ramon 

 on the Rio Chanchamayo in the Perene region at about 10 60' S. lat. 

 and is therefore to be regarded as absolutely typical of impavida. It is 

 characterized by rather dark color with a strong admixture of sooty on 

 the upper parts, by pale creamy or soiled whitish under parts except a 

 buffy chin, and by grayish hind legs. The buff-bellied form from 

 Yurimaguas, previously referred to impavida, is distinguished from the 

 typical form at a glance. 



Holochilus amazonicus sp. nov. 



Type from Itacoatiara, Amazon River, Brazil. No. 20136, Field 

 Museum of Natural History. Adult male. Collected May n, 1913, 

 by Robert H. Becker. Original No. 50. 



Characters: A medium-sized species allied to Holochilus sciureus 

 of eastern Brazil, but larger with a heavier skull and relatively weak 

 dentition. Similar to H. guianae but slightly larger with a longer tail 

 and a heavier more ridged skull. 



Color: Upper parts dull ochraceous buff rather heavily mixed with 

 dusky producing a general effect of cinnamon brown; sides brighter than 

 back and becoming ochraceous buff as they merge with the under parts; 

 forehead slightly duller-colored than back; chest and abdomen heavily 

 washed with clear ochraceous buff, the hairs light neutral gray at the 

 base and broadly tipped with ochraceous buff; throat, inguinal region, 

 and inner sides of legs light buff, the hairs usually self-colored but some- 

 times with grayish bases; ears well-haired, ochraceous buff inside, some- 

 what darker outside; tail uniformly dusky except a very slight subbasal 

 paleness. 



Skull: Decidedly larger and heavier than that of H. sciureus;* 

 rostrum much longer; cheek teeth relatively small and light, about 

 equal in actual size to those of sciureus; supraorbital ridges elevated and 



* Figured by Winge under the name Sigmodon vulpinus (E. Museo Lundii, pt. 

 Ill, pi. II, fig. 5, 1888); see Thomas, Ann. & Mag. Nat. Hist., (6), XIX, p. 495, 

 footnote, 1897. 



