47 



any known genus. Their nearest approach is to those of Helamys : 

 the latter however want the narrowing of the posterior face of the 

 molars in the upper jaw, and the external fold in those of the lower, 

 as well as the oblique position of the latter, which so strikingly cha- 

 racterize the present genus. From Arvicola, which it much more 

 closely resembles in habit, it is at once distinguished by the num- 

 ber of its teeth, and by their much smaller degree of complication. 

 Its specific characters, should the discovery of other species render 

 it necessary so to distinguish it, will probably be found in the fol- 

 lowing phrase : 



Octodon Cumingii. Oct. supra fusco-griseus nigrescenti inter ~ 

 mixtus, infra et ad pedes pallidior ; Cauda suprh et ad apicem 

 floccosam concolore nigrescente. 



In size and shape the animal very closely resembles the common 

 Rat ; but its head is much broader and less elongated, and its tail 

 is uniformly covered with short adpressed rigid hairs, which be^- 

 come longer and more lax as they approach the extremity, where 

 they form a slight floccose tuft. The facial line is regularly and 

 strongly arched, and the muzzle obtusely truncate j the eyes are 

 small, and seated nearly midway between the base of the ears and 

 the nostrils; and the ears are of moderate size, thinly covered both 

 within and without with short adpressed hairs, and rounded at the 

 tips. The whiskers are numerous and rigid, and the longest exceed 

 the head in length. On the body, which is well-proportioned, the 

 fur consists almost entirely of straight hairs, lying flat, and varying 

 from half an inch to an inch in length : they become shorter on the 

 head and beneath the body, and still more so on the tail and limbs. 

 Of the limbs the hinder are somewhat longer, but the disproportion 

 is by no means so great as might be inferred from the saltatory 

 habits of the animal. All the feet have five toes, but the innermost 

 both before and behind is very short, and separated by a wide in- 

 terval from the rest. Except the thumb of the fore feet, which 

 has a short obtuse claw, all the toes are armed with rather long, 

 slightly curved, sharp-pointed claws, partially concealed by long 

 bristly hairs. Of the four outer toes anteriorly the two interme- 

 diate are nearly equal, and the two lateral somewhat shorter; pos- 

 teriorly the three intermediate toes are of nearly equal length, and 

 considerably exceed the outer. The tail, though covered rather 

 thickly with short stiff hairs, is distinctly annulated. 



The general colour of the upper surface and sides is of a brownish 

 gray, intermixed with frequent spots and patches of dusky black. 

 It becomes slightly darker towards the rump ; and the upper surface 

 of the entire tail, together with its under surface for one- third of 

 its length from the tip, is dusky brown approaching to black. The 

 under surface is dusky gray mixed with a shade of brown, lighter 

 beneath the base of the tail, and deeper on the breast and neck, 

 where it is nearly of the same general hue with the upper surface 

 and head. The ears are dusky, with a few stiff gray hairs at their 

 base anteriorly, and some whitish hairs on their inner surface. The 

 shorter whiskers are for the most part white, and the longer black. 



