iQ2 FIELD MUSEUM OF NATURAL HISTORY ZOOLOGY, VOL. X. 



stated by Waterhouse, has very large ears and a more uniform colora- 

 tion than P. pictus and P. decoloratus. The ear in the single topotype 

 available measures approximately 25 mm. in length whereas in the 

 largest of eight specimens of the species here described it measures 

 only 1 8 mm., a difference of nearly forty per cent. Specimens from 

 San Antonio and Crucero, Peru, are somewhat brighter in color than 

 those from Tirapata, but are otherwise similar. 



Akodon aerosus baliolus subsp. nov. 



Type from Inca Mines, Inambari River, Peru. Adult male. 

 No. 20108 Field Museum of Natural History. Collected Aug. n, 1900, 

 by H. H. Keays. 



Characters: Similar to Akodon czrosus as represented by specimens 

 from northeastern Peru (Moyobamba), but darker, more blackish, in 

 color. General color above blackish bister or mummy brown, the rump 

 rather more blackish than the anterior parts; lower parts correspond- 

 ingly dark and showing less contrast than in czrosus. Skull averaging 

 rather shorter with broader braincase and shorter nasals; otherwise 

 similar to that of arosus. 



Measurements: Type: Total length 190; tail 83 ; hind foot (dry) 25. 

 Skull of type : Greatest length 2 8 ; basilar length 22.7; zygomatic breadth 

 14.7; breadth of braincase 13.4; nasals 9.8x3.3; interorbital constric- 

 tion 5.7; palatine foramina 5. 9 X 2.2; upper toothrow 4.8. 



Remarks: The slight characters distinguishing this form are con- 

 stant in the small series examined and the great distance between its 

 range and that of typical cerosus lends probability to the inference that 

 larger series would be equally constant. In the thousand miles or more 

 between southern Ecuador, the type locality of cerosus, and southern 

 Peru, where the present form is found, there is much country not yet 

 visited by naturalists and records of this species are few, but there can 

 be little doubt that it has nearly or quite continuous range along the 

 east base of the Andes from Ecuador to Bolivia. 



Dasyprocta nigriclunis sp. nov. 



Type from Sao Marcello, upper Rio Preto, Bahia, Brazil. No. 20746 

 Field Museum of Natural History. Adolescent female. Collected 

 March 23, 1914, by Robert H. Becker. Original No. 559. 



Characters: A very distinct species with jet black nape and rump 

 and hairy ferruginous ears; hairs of nape elongated to form a slight 

 nuchal crest; size medium; general relationship probably with Dasy- 



