284 Mr. 0. Thomas on 



Cavia mcenas, sp. n. 



Nearly allied to C austrah's, but larger. General colour 

 dull buffy fawn, the hairs pale slaty basally, with subterminal 

 buflfj bands and black tips. Ejes with well-marked whitish 

 rings. Hairs on inner side of ear and on the patch behind 

 its posterior base whitish. Under surface buffy white, not 

 sharply defined, the hairs slaty grey basally. Uppersides of 

 hands and feet dull whitish, tending towards fawn mesially. 



Skull with a much longer and more parallel-sided muzzle 

 than C. austrah's, the nasals practically as broad in front as 

 behind ; interorbital region flat, little ridged, its edges more 

 nearly parallel than in C austrah's. Lacrymals as in that 

 species. Palatal foramina very long, uniting with the in- 

 cisive fissures, not of the characteristic triangular shape of 

 those of 0. austrah's. 



Upper incisors vertical, not thrown forward; white in 

 front. Talon of m.^ long, about equal in extent to the 

 second lamina of that tooth. 



Dimensions of the type, in skin : — 



Head and body (evidently stretched) 265 millim.; hind 

 foot, without claws 41, with claws 45. 



Skull : tip of nasals to bregma 35*5 ; greatest breadth 30 ; 

 nasals 18'7 X 6*5 ; interorbital breadth 11"1 ; palate length 

 from henselion 22"6 ; diastema 12'5 ; palatal foramina 10 X 3 ; 

 length of upper molar series 12"2 ; lower jaw, back of condyle 

 to incisor-tip 37. 



JIab. Chilecito, Rioja, 3200 metres. 



Type B.M. no. 96. iO. 7. 12. Collected and presented by 

 Dr. F. P. Moreno, of the La Plata Museum. 



This species is evidently the North-Argentine representa- 

 tive of C. australis, to which species alone it is nearly allied 

 and from which it may be distinguished by its more buffy 

 colour, longer nasals, more vertical incisors, and longer 

 palatal foramina. Besides the type, the Museum possesses 

 an example in spirit from Mendoza of what appears (allowing 

 for the cranial variation usual in the group) to be the same 

 form, while a third example — a skin — was said to have come 

 from " Chili " ; but it seems probable that this statement is 

 erroneous. 



(11.) 



"When in Argentina in the early part of 1896 I was given 

 by Dr. C. Spegazzini, of the La Plata Institute of Agronomy, 

 four specimens in the flesh of a Tuco-tuco, which he had 



