1902.] NEW BOLIVIAN ROBEXTS, 115 



of the deep internal enamel infolding found in that genus. The 

 premolar rounded, triangular in section. Lower teeth oval in 

 section, a slight median constriction on each side of m^ and m.^. 



This genus is, no doubt, closely allied to Octodon, of which it is 

 a highland representative. 



Neoctodon simonsi, sp. n, (Plates VIII. & IX. figs. 8-12.) 



General appearance very much as in the North- American 

 Neotoma cinerea, strikingly difierent, by paler colour, whiter 

 belly, and longer, more bushy tail, from either of the species of 

 Octodon, Fur soft and fine, hairs of back about 22 mm. in length. 



General colour above pale drab-grey, grizzled with black. Sides 

 clearer drab. Under surface snowy white, well defined laterally, 

 where it extends rather high up ; the bases of the hairs slaty 

 except on the chin. Front of upper lip hairy, not grooved. Face 

 coloured like the back, paler on the sides of the muzzle and 

 cheeks ; no definite mai'kings round eyes. A few longer vibrissfe 

 placed just above eye, and a more prominent tuft of them between 

 eye and ear. Ears large, shaped about as in Octodon, finely 

 covered with short greyish hairs ; a distinct tuft of white hau's at 

 their anterior bases. Outer sides of arms and legs like back, 

 inner sides like belly; upper surface of hands and feet pure 

 white, the hairs stifi" and elongated terminally, so as to surpass 

 the claws ; palms and soles entirely naked, strongly granulated, 

 with projecting cushions, on which the pads are so small as to be 

 scarcely perceptible among the granulations ; under the heel the 

 surface is comparatively smooth ; poUex with a broad flat nail ; 

 hallux short, with a claw, its tip falling some way short of the 

 base of the second digit ; fifth toe, without claw, reaching to the 

 end of the basal phalanx of the fourth. Scrotum naked. Penis 

 with a bone, which is flattened, tapering, though not to a point, 

 about 15 mm. in length. Tail nearly as long as the head and 

 body, thick, cylindrical, well clothed throughout with hairs, which 

 increase in length to the end, where they may be fully an inch 

 long. In colour the tail is brownish black above and at the end, 

 white proximally on the sides and below ; the hairs of the pencil- 

 end are usually pale brown or even sandy brown, but this appears 

 to be an effect of bleaching, more or less dependent on the season, 

 as is the case in the British Squirrel. 



Skull and teeth as shown in the figures. 



Dimensions of the type, measured by Mr. Simons in the 

 flesh : — 



Head and body 184 mm. ; tail 152 ; hind foot, s. u. 36, c. u. 38 ; 

 ear 32. 



Skull — greatest length 46, basilar length 38, greatest breadth 

 24; nasals 17 x 5'8 ; interorbital breadth 10; length of frontal 

 suture 13-5; breadth of brain-case 18*5; palate length 17-2; 

 diastema 12; palatal foramina 4'8x2'4; length of upper tooth- 

 series (crowns) 8*3 ; length of bulla 13; breadth of basi- occipital 

 on suture 2 "6. 



8* 



