Mammals from Jujtii/. 193 



This Akodon was originally doscribod as a subspecies of 

 A. purr, but is shown by better njaterial to have a somewhat 

 lari^ei' skull with more angular supraorbital edges, and to be 

 distinctly more hypsodont than that animal — in Eact, as much 

 so as in the large A. simulator^ I therefore recognize it as 

 specifically distinct. 



A com[)lete male skull lias a greatest length of 25*5 mm. ; 

 condylo-incisive length 23"2. 



14. Ctenomi/s sjjivanus utibih'.tj subsp. n. 



? . 713, 715. Yuto, Rio San Francisco. Alt. 500 m. 



"Fouiul among woods; sandy soil." — E. B. 



Size and general characters of true sylvamis, but lighter 

 and with white patches on under surface. 



Colour above near " snufF-brown," but rather darker, tin; 

 median dorsal line blackened in the paratype, but not so in 

 the type. Under surface iu general scarcely lighter, but in 

 both specimens there are well-marked axillary white spots 

 ami cons})icuous inguinal patches. Sides of muzzle scarcely 

 blackened. Hands, feet, and tail more hairy than in sylca- 

 nus, less than in biidhii, the hands and feet white, the tail 

 blackish for its proximal two-thirds, then white. 



Skull about as in si/lvanus, but in the available specimens 

 the interparietals are larger, about equalling those of hudhiij 

 and the palatal notch ends opposite the middle instead of the 

 front edge of m"^. 



Dimensions of the type : — 



Head and body 190 mm, ; tail 65 ; hind foot 34*5. 



Skull : median length 45*7 ; condylo-incisive length 45 ; 

 zygomatic breadth 28*7 ; nasals 16-2 x 7'8 ; interorbital 

 breadth 10'2; breadth across brain-case 19'5; bimeatal 

 breadth 28-5; palatilar length 20-3; dental length 26; 

 upper tooth-series (crowns) 9*8. 



Type. Adult, but not old, female. B.M. no. 20. 1. 7. 114. 

 Original number 715. Collected 24th July, 1U19. 



This tuco-tuco would seem to be a less saturate form than 

 true sylvanus, inhabiting more open woods, with the soil 

 " arenoso " instead of "vegetal" — sand instead of humus. 

 Its general tone is rather lighter, its muzzle is conspicuously 

 so, while its prominent white axillary and inguinal patches 

 afford the most obvious means of distinction, as there are 

 none at all in aylvanus. Both forms are no doubt nearly 

 allied to Inidini, but from tliat the distinction of utibUis in 

 ground-colour, and especially in tliat of the lower surface, is 

 markedly greater. Both sytcanns and nt Unit's occur at about 

 500 m., while bud'uil conu's (rom 2(J00 m. 



