188 Fretp Museum or Naturat History — Zoéxrocy, Vor. 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‘ 15.7; combined length 
ms? 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 Perené region at about 10° 60’ S. lat. 
and is therefore to be regarded as absolutely typical of zmpavida. 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 zmpavida, 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 i1, 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 
Pigured by on under the name Sigmodon ys (E, Museo Lundii, pt. 
at I ); at. 
* 
III, p , fig. 5, 1888); see Thomas, Ann. & Mag. Hist., (6), XIX, p. 495, 
footnote, 1897. 
