1903.] Allen, New Rodents from Patagonia. 193 



being plumbeous black for the basal four fifths, with an apical band of 

 brownish fulvous, and many longer black hairs intermixed; sides 

 much paler and more fulvous, the fulvous increasing in intensity along 

 the lower border; ventral surface soiled white, the fur being basally 

 very dark plumbeous and broadly tipped with yellowish white; ears 

 dark brown on both surfaces and very thinly haired, the surrounding 

 fur concolorous with that of the anterior dorsal surface; sides of nose 

 and lower border of cheeks whitish gray with a faint tinge of yellowish; 

 soles naked except the posterior third, dark flesh-color; upper surface 

 of fore and hind feet pale flesh-color, nearly white; tail one third or 

 less than one third of the total length, well clothed, dusky brown 

 above, sides and below white. 



Measurements. Total length, 175; tail vertebra?, 60; hind foot, 

 26. Three other specimens (young adults) measure: Total length 

 160 (150165); tail vertebrae, 57 (50-60); hind foot, 25 (2525). 



Skull. Long and narrow, the interorbital and rostral portions 

 especially elongated; post-palatal fossa narrow and v-shaped, but not 

 quite so narrow and pointed in front as in Reithrodon cuniculoides; 

 front border of zygomatic plate as in Phyllotis, Oryzomys, etc., lacking 

 the pointed superior process seen in Reithrodon and Sigmodon; bullae 

 small and pointed, as in Phyllotis; upper incisors deeply grooved; 

 molars brachyodont as in Phyllotis, but very broad and heavy, not 

 hypsodont as in true Reithrodon; lower jaw short and heavy to sup- 

 port the thickened molars; posterior end of lower incisor encapsuled, 

 forming a prominent process on the outer sides at the base of the 

 condyloid process. Dimensions (type): Total length, 30.5; basal 

 length, 26.5; zygomatic breadth, 17.5; interorbital breadth, 3.5; 

 width of brain case, 14; length of nasals, 14; palatal length, 14.5; 

 palatal foramina, 8 ; diastema, 8.5; upper molar series, 5.2; width of 

 first molar, 1.8; lower jaw, length (inner base of incisors to posterior 

 border of condyle) , 18; height at condyle, 15; lower molar series, 5.5. 



Represented by four specimens, an adult female that had 

 suckled young, and three younger specimens, nearly adult, all 

 taken by Mr. Peterson in the Cordilleras at the head of the 

 Rio Chico de Santa Cruz, Feb. 8-14, 1897. These specimens 

 are all quite similar in coloration, except that the younger 

 ones are grayer than the adults, with much less fulvous suf- 

 fusion and with very little fulvous on the flanks and ventral 

 surface. 



This species finds its nearest ally in Euneomys chinchilloides 

 (Waterhouse), known thus far only from Tierra del Fuego, 

 which it apparently closely resembles in size and coloration. 



[April, igoj.] 3 



