156 On Two new Rodents from Argentina. 



cinnamon. Muzzle darker brown, but not definitely blackened. 

 Area round ears dark slaty. Hands thinly haired, whitish ; 

 feet almost naked, the few fine hairs white. Tail practically 

 naked, its minute hairs brownish white. 



Skull not distinguishable by any definite character from 

 that of C. budini. A separate bone present at the front of 

 the parietal in the only specimen in which this part has not 

 been broken. Interparietal distinct, but small. Palate 

 ending opposite the front edge of m 8 . Bullae about as in 

 budini. 



Teeth as in budini, though the incisors may be slightly 

 more opisthodont (angle, 100°-103°). 



Dimensions-of the type : — 



Head and body 200 mm. ; tail 73 ; hind foot 34 ; 

 ear 8. 



Skull : upper median length 44 - 5 * mm. ; condylo-incisive 

 length 45*; gnathion to back of bulla 46"5*; zygomatic 

 breadth 27 ; nasals 16 x 82 ; interorbital breadth 10'5 ; 

 palatilar length 20; upper tooth-series (crowns) 10'3 ; 

 greatest diameter of p* 4c'2. 



Hub. as above. 



Type. Adult female. B.M. no. 19. 7. 25. 4. Original 

 number 396. Collected 20th November, 1918. 



The remarkable note made by Sr. Budin on the labels that 

 this species is found in thick forest is confirmed by the 

 following extract from one of his letters (translation) : — "In 

 spite of having been ill I have secured some specimens of 

 Tuco-tuco which certainly will interest you very much, and 

 I believe are new. They are in general of a dark plumbeous 

 colour, and the largest measures 200 mm. in length. I have 

 been surprised to find these animals in the thickest woods, as 

 I believed that Tuco-tucos only inhabited open country. 

 They are very rare, besides being exceedingly shy and diffi- 

 cult to trap, and it has given me great trouble to get this 

 small series/' 



In spite of this great difference in habits, which is as great 

 a surprise to me as it was to Sr. Budin, there is unexpectedly 

 little essential difference between C. sylvanus and C. budini, 

 the different colour and the more naked feet and tail being 

 practically the only distinguishing points, the skulls being 

 almost precisely similar. But as not one of the seven skulls 

 has escaped damage in the trapping, more perfect skulls may 

 in the future indicate some cranial difference not now 

 perceptible. 



* These measurements were taken before the skull was separated for 

 cleaning, it having' been broken in half by the trap. 



