244 On neio South- American Rodents. 



0,vymycterus platejisif, sp. n. 



Closely allied to 0. rufus, o£ which I take a specimen 

 from Goya, Coirientes, as representative. Fur thicker and 

 woollier, hairs o£ back about 13-14 mm. in length. Colour 

 darker arid deeper red than in rufus, distinctly darkened 

 alon^^ie crown, nape, and middle line of back by blacidsh, 

 tU^ corresponding area in rvfus being greyish ; cheeks, sides, 

 '^and rump deep ferruginous; belly dark "cinnamon-buff"; 

 chin white ; hands and feet mixed brown and whitish, 

 browner on the metapodials. Tail uniformly dark brown. 



Skull, in six adult and old specimens, uniformly shorter 

 than in rufus, but nearly equalling it in breadth. Tip of 

 nasals distinctly trumpet-shaped, more so than in rufus. 

 Brain-case shorter and proportionally broader. Mesopterygoid 

 foss« broader anteriorly, markedly narrowing behind. Molar 

 series shorter. 



Dimensions of the type (measured in flesh) : — 



Head and body 140 mm.; tail ]11; hind foot 28; 

 ear 16*5. 



Skull : greatest length 36 ; condylo-incisive length 33'2 ; 

 zygomatic breadth 17*2; nasals 13 ; interorbital breadth 6'2 ; 

 breadth of brain-case 14'4 ; palatilar length 14*8 ; palatal 

 foramina 8 ; upper molar series 5*4. 



Hah. Etisenada, La Plata. Sea-level. 



Tijpe. Old male. B.M. no. 99. 10. 4. 1. Original 

 number 165. Collected 24th June, 1896, by Dr. C. Spe- 

 gazzini. Seven specimens. 



This Oxymycterus differs externally by its darker and 

 richer colour and the distinct blackening along its head, 

 nape, and fore back from its near ally 0. rufus, whose sides 

 are more bufFy and whose head and foreback are more 

 greyish. The skull is shorter, with more trumpet-shaped 

 nasals, and the molars are smaller. 



The specimens of this animal, in company with those of 

 Ctenomys talarum, were brought to me in the flesh on the 

 last day of my stay in La Plata by the well-known botanist 

 Dr. C. Spegazzini, who had shot them under the Tala trees 

 on the Rio Santiago, Ensenada. 



The type of 0. nasutus, Waterh., from Maldonado, on the 

 opposite side of the La Plata estuary, is so young that its 

 full size cannot easily be gauged ; but examples from E,io 

 Grande do Sul which I refer to that species are conspicuously 

 smaller than 0. platensis. 



