EINAR LÖNNBERG, MAMMALS FROM ECUADOR. 21 



Cli. hoffmanni from Central America and Ch. didactylus (ma- 

 terial from Venezuela). 



With regard to the size of the animal the Choloepus from 

 Napo may be regarded as one of the largest forms, and pro- 

 bably about equal to Ch. florenciae Allén in this respect. 



For the comparison of the skull with that of other spe- 

 cies the by J. A. Allén published photographic reproduc- 

 tions^ of the skulls of the six recognised forms of Choloepus 

 are very useful. If these figures are examined, it is easily 

 seen, that with regard to their general shape they can be 

 divided into two groups. In one of these, which is consti- 

 tuted by Ch. florenciae and Ch. andinus (both described by 

 Allén), the skull is rather longish, so that the breadth across 

 the postorbital processes in contained about twice in the 

 oceipitonasal iength of the skull. In the remaining group 

 the said breadth is considerably more than half the oceipi- 

 tonasal Iength. The Sloth from Napo belongs, as the below 

 recorded measurements prove, to the group with longish 

 skulls. It has most resemblance with Ch. florenciae and 

 many of the dimensions recorded by Allén for this species 

 are very similar to those of the present specimen. The con- 

 dylobasal Iength of both is the same, but all dimensions ex- 

 pressing breadth are larger in the animal from Napo especi- 

 ally zygomatic, interorbital breadth -indexes and the breadth 

 of the snout ; the palate is longer; but the diastema shorter; 

 the coronoid considerably higher and so on. A comparison 

 with Allen's figure of the skull of Ch. florenciae reveals 

 several other important differences. The rostrum of the 

 latter is not only narrower across the canines, but also slen- 

 derer in other respects than is the case in the Ch. napensis. 

 Thus the shortest distance between for. lacrymale and the 

 margin of the nasal opening is in the latter less, but in the 

 former more than the height of the rostrum on a level with 

 the canines. Squama occipitalis is in Ch. napensis practically 

 quite vertical, but in Ch. florenciae rather strongly sloping. 

 The posterior margin of the bony palate is in Ch. napensis 

 almost square only little rounded at the sides and situated 

 well behind the molars, while the same in Ch. florenciae 

 shows a deep angle, which reaches with its point forward to 



1 BuU. Amer. Mus., Vol. XXXII. 1U13. 



