On a new Tuco-tuco from Tucuman. 243 



XXX. — A nevj Tuco-tuco from Tucuman. 

 By Oldfield Thomas. 



(Piiblishetl by peruiissiou of the Trustees of the British Museum.) 



Ctenomys occultus, sp. n. 



A small species nearly allied to G. juris. 



Size rather less than in juris. Colour rather a warmer 

 tinge of brown, more as in C. hergi and latro; upper surface 

 glossy cinnamon-brown with some vague darkening on the 

 crown^ but without a definite blackish forehead. Under 

 surface broadly washed with pale drabby, the chin and throat 

 stronger drabby ; some specimens are more whitish below, 

 while among the examples of juris some are inclined to be 

 drabby ; but on the average occuUus is decidedly more 

 drabby, especially anteriorly, tha.n juris. 



Skull agreeing with that ol juris in its small bullae, proodont 

 incisors, and the presence of a small sharp-edged ledge pro- 

 jecting over the orbital fossae, the notch in front of these 

 ledges shorter, sharper, and more abruptly cut out than in 

 other species. BuUse slightly larger than those of juris, 

 though agreeing essentially with them ; in hergi and fochi 

 they are decidedly larger than in either. Zygomata widely 

 spaced, their middle region markedly more convex outwards 

 than in juris. Palatal foramina with the small median ad- 

 ditional foramen just in front of them much smaller and 

 less conspicuous — indeed^ hardly perceptible in some speci- 

 mens. Palation level with the middle of ??r. Bulla3 averaging 

 slightly larger than in juris, though agreeing essentially with 

 them. 



Incisors rather proodont, index about 102°-104°. Molars 

 smaller than those of C. juris. 



Dimensions of the type : — 



Head and body 138 mm. ; tail 55 ; hind toot 26*5. 



Skull : median length 38'7 ; condylo-incisive length 37'8; 

 zygon)atic breadth 2b'2 ; nasals 12 5 ; interorbital breadth 8*7 ; 

 least breadth across brain-case IG'5 ; bi-meatal breadth 24 ; 

 palatilar length 17" 7. Upper tooth-series (crowns) 7*2 ; 

 diagonal diameter uf p* 3 ; breadth across outer crowns of 

 ;/ 7*8. 



Hab. Southern part of Tucuman Province. Type and 

 three other specimens from Monteagudo, about 80 km. S.E. 

 of Tucuman City ; one specimen from Li Madrid, 15 km. 

 further in the same direction. 



