Two new Argentine Rodents. 285 



obtained at " Las Talas " *, a district along the lower part of 

 the Santiago River, near Ensenada, the port of La Plata. 

 This animal, when describing Ctenomys Perrensi^ I referred f 

 with some doubt to Dr. Nehring's Gt. mi'nutus, originally 

 from Mundo Novo, Rio Grande do Sul. Thanks to the kind- 

 ness of Dr. Nehring, I now possess a careful drawing of the 

 largest of the three skulls he founded that species upon, and 

 am therefore able to make a comparison between Ct. minutus 

 and the La Plata animal. From the drawing it appears to 

 me evident that Dr. Nehring's specimens were immature — so 

 much so, indeed, that I doubt if the full-grown animal is any 

 smaller than the Uruguayan Ct. torquatuSy Licht. In any 

 case, however, the Ensenada Tuco-tuco, of which an old male 

 barely exceeds in size the immature Ct. minutus^ besides 

 differing in other characters, must be considered as a distinct 

 species. 



Ctenomys talarum, sp. n. 



Size very small ; form, as judged by skull, more slender 

 than usual. General colour above very dark, the usual 

 bufFy or clay-coloured subterminal bands on the hairs being 

 much hidden and obscured by their unusually broad black 

 tipping, the whole of the back being as dark as the very 

 darkest patches on the spine of Ct. Perrensi. Centre of face 

 nearly or quite black. Cheeks like back ; a small but well- 

 marked whitish patch just at the lower edge of the ear. 

 Under surface pale, almost exactly " cream-buff" of Ridgway, 

 the chest very faintly darker ; white axillary and inguinal 

 patches very small. Sparse hairs of hands and feet whitish 

 buff. Tail blackish brown above, pale bufFy below. 



Skull much lighter and more slender than in any other 

 species known to me. Muzzle narrow, parallel-sided. Nasals 

 broad, rapidly narrowing backward. Interorbital region 

 narrow, the postorbital processes delicate. Brain-case low 

 and flattened. Interparietal small, broader than long. Bullse 

 narrow. 



Incisors less broad than in the allied species, their faces 

 as usual deep orange-yellow above and below. 



Dimensions of the type (an adult male), taken by myself 

 in the flesh : — 



Head and body 172 millim. ; tail 55 ; hind foot, without 

 claws, 30. 



Skull : basal length 40*3 ; basilar length 38 j zygomatic 



* So called from the Tala trees ( Celtis tola) which grow in the locality 

 t Ann. & Mag. Nat. Hist. (6) xviii. p. 312 (1896). 



