19 Bulletin American Museum of Natural History. [Vol. XIX, 



with the tail one half shorter and fore claws large, fossorial. Above 

 dark yellowish brown ; tmderparts whitish gray, the plumbeous under 

 fur tinging the otherwise whitish surface; top and sides of nose dark 

 grayish brown, without any tinge of yellow or rufous; ears very small, 

 scarcely reaching the surface of the short fur, concolorous with the 

 enclosing fur; tail very short, but little exceeding the length of the 

 hind foot, very thickly clothed, dark brown, only slightly lighter below 

 than above; upper surface of the feet grayish brown, the toes lighter, 

 yellowish white; soles naked, dark flesh-color. 



A second specimen is exactly similar in coloration, except that the 

 ventral surface has a slight wash of buff, apparently due to staining. 



Measurements. Total length (type), 138; tail vertebrae, 28; hind 

 foot, 21 ; longest fore claw, 6. Skull, total length, 27.6; basal length, 

 23.6; zygomatic breadth, 12.5; width of brain case, 12; interorbital 

 breadth, 5; length of nasals, 10.5; palatal length, 10; palatal fora- 

 mina, 5; diastema, 6.3; upper molar series, 3.5; length of lower jaw 

 (inner base of incisors to posterior border of condyle), 15; height at 

 condyle, 5.5; lower molar series, 3.4. 



Represented by two specimens a skin and skull, and a 

 skin and skeleton collected on the Pacific slope of the Cor- 

 dilleras, at the head of the Rio Chico de Santa Cruz. 



Externally Oxymycterus microtis is a miniature of Akodon 

 macronyx with a relatively much shorter tail. It exactly re- 

 sembles in coloration above and in the texture of the pelage 

 Oxymycterus lanosus, but the latter has whiter under parts, 

 is very much smaller, has a much longer tail, and small, non- 

 f ossorial claws ; but the skulls of the two are very similar in 

 general contour, differing only in size and slightly in details. 

 0. microtis thus combines the large fossorial claws of the 

 Akodon macronyx group with the cranial characters and weak 

 dentition of the 0. lanosus type. The narrow line separating 

 Akodon and Oxymycterus is thus still further narrowed by the 

 present annectent link. 



Reithrodon cuniculoides obscurus, subsp. nov. 



Type, No. 3, Colburn Coll., $ ad., Punta Arenas, Patagonia, Jan. i, 

 1898; A. E. Colburn. 



Similar to Reithrodon cuniculoides, but darker throughout, the upper 

 parts dark brown, varied with black- tipped hairs and suffused with 

 fulvous, the sides yellowish, and the ventral surface brownish ochra- 

 ceous; inner side of thighs and anal region whitish; top of head 



