small Miimmah from Catamarca. 117 



Dimonsion3 of tlio type (measuioil in flesli) : — 



Hend and body 98 rara. ; tail 75; hind foot 22 ; 

 ear IS. 



Skull: greatest lonj;th 275; coiidylo-incisive length 26 ; 

 zyj^om.itic hreadtli ll*3 ; nasals 10 ; interorbital breadtb 5 ; 

 breadth of brain-case 12 ; nalatilar lengtli 12"2 ; palatal 

 foramina 7 ; postforaminal palate 4; npper molar series 4*8. 



A single very olil male, no. 225, is decidedly larger, the 

 head and body 115 and the skull 30*5 mm. in length. 



Ila/>. as above. 



Type. Adult male. B.M. no. 18. 11. 11. 57. Original 

 number 222. Collected 24th June, 1918. 



"Caught under rocks among roots of trees." — E. B. 



While there is no doubt that A. varius, A. simulator^ and 

 the present form are so closely allied that they may hereafter 

 be shown to represent subspecies of one widely-spread species, 

 I provisionally give a binomial name to this animal until such 

 time as fuller material shows the true relationship between 

 the different members of the group. 



7. Akodon arenicola, Waterh. 

 ? . 228. 



8. Ctenomt/sfochi, sp. n. 



,?. 247; ?. 248,256, 265. 



Closely allied to C. bergi, Thos., of Cruz del Eje, Cordova, 

 with which it agrees in size. General colour, however, more 

 drabby, the tone near " buflfy brown'' of Ridgway, while that 

 of beiyi is more like " sayal brown," Hairs of under surface 

 washed with paler drabby, the hairs everywhere slaty at base, 

 while those of the interramiu are in bergi buffy to their roots. 

 Dark aroa on muzzle and crown nearly black, much darker 

 than ill birgi. 



Skull like that of C. bergi, except that the bullfe are 

 uniformly (f<iur sjiecimens as compared with three) rather 

 more inflateil, the line connecting the antcro-internal angle 

 with the meatal tube more dislinclly convex forwards, as 

 viewed from above. 



Dimensions of the type : — 



Head ami body 1G2 mm. ; tail 76 ; hind foot 30. 



Skull : greatest diagonal longih 39 ; comlylo-incisive 

 length 37; zygomatic l)riadth 23; nasals 11'2 x 5*2 (in 

 another specimen 12*5 x5'7); least breadth across brain- 

 case 17; meatul breadth 24'5 ; bulla, greatest diagonal 

 diameter 15*2, breadth at right angles to last (exclusive of 

 meatal tube) 8"5 ; upper molar series (crowns) 8 ; alveoli .S 8, 



