38 PATAGONIAN EXPEDITIONS: ZOOLOGY. 



His description of the color of C. fueginiis indicates a pale, ashy gray 

 animal very different from that inhabiting the Cordilleras, but quite similar 

 to C. magellanicus, the type locality of \\hich is Cape Gregory, on the 

 northern side of the Strait of Magellan. In view of its insular habitat, 

 and in the absence of proper material for comparison, it seems best to give 

 the species provisional recognition. 



Ctenomys robustus Allen. 



(Plate VII, Figs. 2 and 3, Skull.) 



Ctenomys robnshts Allen, Bull. Am. Mus. Nat. Hist., XIX, 185, May 9, 

 1903. Rio Chico de Santa Cruz, near the Cordilleras, Patagonia. 



Pelage soft, short, somewhat lustrous. Above deep yellowish brown, 

 varied with blackish, the hairs being dark slaty plumbeous for the basal 

 two thirds, with a subterminal band of dark rusty yellow, and a very 

 short black tip, with longer blackish-tipped hairs sparsely intermixed ; 

 below deep brownish ochraceous ; ears dusky brown, barely projecting 

 above the fur ; upper surface of fore and hind feet dingy yellowish gray ; 

 tail well clothed with fine soft hairs, forming a slight pencil at the tip, 

 yellowish gray, dusky at the tip above. 



Other specimens vary from the above in being a little lighter or a little 

 darker, both above and below. Tail variable in color, often wholly without 

 any dusky median line above or any dusky tip ; generally there is a very 

 narrow median dusky line, extending from the tip anteriorly for a part or 

 the whole of the length of the tail ; in a few specimens it is strongly 

 developed, broadens and increases in blackness towards the tip, and in 

 rare cases the whole tip is black, with a short black stripe on the lower 

 surface of the apical fourth or third of the tail. 



Young examples differ from the adults in the general tint being duller 

 and the pelage less lustrous. 



Measurements. — Type: Total length, 290 mm. ; tail vertebrae, 73; hind 

 foot, 40. Nine adult males measure as follows : Total length, 303.5 (290- 

 322 ; only one above 310, and only two above 298) ; tail vertebrae, 81.5 

 (73-88) ; hind foot, 40.5 (40-42). Five adult females; Total length, 275 

 (256-300; only one above 280) ; tail vertebrae, 75 (70-80) ; hind foot, 37 



(35-40). 



Skull, type : Total length, 52.5 ; basal length, 47 ; zygomatic breadth, 

 30; interorbital breadth, 10; mastoid breadth, 29.5; length of nasals, 20; 



