132 Mr. O. Thomas on 



7. Ctenomys luteolus, Thos. 



t? . 415, 416, 423, 426, 427, 432, 433, 442, 493 ; ? . 407, 

 409, 413, 424, 431, 440, 441, 445, 489, 492. Abrapampa, 

 3500 m. 



This tuco-tuco was described in 1899 on a single specimen 

 from the " Cordillera of Jujuy" — therefore very much the 

 same locality as the present. 



The coloration, notably the whitish or white nose, proves 

 to be absolutely constant throughout this fine series, while 

 in the skull I find that the anterior cheek-teeth are slightly 

 less in diameter than in opimus, and the skull itself does not 

 seem to attain so great a size. I consequently now use the 

 name in a binomial form. 



8. Abrocoma cinerea, sp. n. 



tf. 540. Cerro Oasabindo, 4800 m. (=15,600'), 22nd 

 March, 1919. B.M. no. 19. 8. 2. 29. Type. 



A grey mountain Abrocoma, with very short tail and feet. 



Size about as in A. murrayi, smaller than in A. bennettii. 

 Fur very soft and fine; hairs of back just over 20 mm. in 

 length. General colour above light grey, slightly paler than 

 " pale neutral grey " ; lighter on sides ; belly broadly washed 

 with greyish white. Ears very large, almost naked, brown. 

 Forearms and lower legs buffy whitish ; hands and feet 

 silvery white. Soles of the same crenulated structure as in 

 the other species, but the feet themselves disproportionally 

 small, only about half the length of the skull. Tail also very 

 short, about half as long as in the other species, uniformly 

 closely haired, not crested, pale neutral grey above, white 

 below. 



Skull showing an extreme development of the differences 

 that separate A. murrayi from bennettii. A. murrayi has a 

 bowed skull, with small incisors and large bulla* ; in A. ci- 

 nerea the skull is more bowed, has still smaller — indeed, 

 quite abnormally small — incisors and still larger bulla?. 

 Otherwise there is little to distinguish the two, and the struc- 

 ture of the molars is quite the same in all. Height of middle 

 part of zygomata greatest (4*5 mm.) in bennettii, 3*4 in 

 murrayi, least (2*8 mm.) in cinerea. Posterior palatine 

 foramina quite small, not the conspicuous opening found in 

 the other species. 



Dimensions of the type : — 



Head and body 192 mm. ; tail 70; hind foot 27'5; 

 ear 29-5. 



