Eastern Buenos Ayres, &c. 213 



specimens. Under surface pale tl wood-brown/' not so 

 creamy as in talarum ; marked white patches present in the 

 axilla, on the inner sides of the hips, and on the centre of the 

 inguinal region ; in talarum a minute axillary patch is alone 

 present. Tail markedly longer than in talarum, brown above, 

 paler below. 



Skull very much as in talarum, but distinct parietal 

 masseteric ridges are perceptible, which is not the case in 

 talarum. 



Dimensions of the type (measured in the flesh) : — 



Head and body 174 mm. ; tail 70 ; hind foot 28. 



Skull: condylo-basal length 41*5 ; zygomatic breadth 25*5 ; 

 nasals 14x6"8; interorbital breadth 9*2; mastoid breadth 

 on lips of meatus 25 ; upper molar series (alveoli) 9*5. 



Tiffie. Adult male. B.M. no. 9. 12. 1. 29. Original 

 number 2081. Collected 14th December, 1908. 



This Tuco-tuco differs so much on the average from the 

 form which 1 found at La Plata that it should apparently be 

 distinguished subspecifically, The colour characters are not 

 absolutely constant, one specimen in ten haviug a black 

 frontal region and darkened back, while one example of 

 talarum has the brownish under surface of antonii. In tail- 

 length the Aj6 form measures from 61 to 70 mm., while in 

 the La Plata animal the tail is 52-57 in length. 



From C. azarce, the Tuco-tuco of the Central Pampas of 

 Buenos Ayrts Province *, C. talarum, in either subspecies, 

 is readily distinguishable by its much narrower bullae. 



" Ploughed out in sandy potrero." " Caught running 

 about in garden."— C. H. B. G. 



The following Ctenomys also seems to need description : — 



Ctenomys fodax, sp. n. 



Allied to Ct. osgoodi, Allen f, but rather larger and with 

 various cranial differences. 



Size among the largest of the genus. Fur rather softer 

 and looser than in osgoodi. Colour above varying from palo 

 cinnamon to isabella, but averaging more cinnamon than in 

 the allied species. Tail and hind feet both longer than in 

 that animal, but owing to the want of good flesh-measure- 

 ments the difference cannot be very exactly stated. 



* Cf. Ann. & Mag. Nat. Hist. (7) xii. p. 243 (1903). 



t Ct. robustus, Allen, Bull. Am. Mus. N. H. xix. p. 185 (1901); 

 Mainm. Southern Patagonia, p. 38, 1905 (nee Phil.). Ct. osyoodi, id. 

 Mamm. S. Pat. p. 191 (footnote). 



