Dec. ii, 1879] 



NATURE 



x 37 



belongs to the order Rodentia. It differs, however, from 

 all the members of this group by characters of consider- 

 able importance ; I may even say that, by some pecu- 

 liarities of structure it departs from all other mammals, 

 and that we find in it anatomical arrangements of which 

 we have hitherto had examples only in the class of 

 reptiles.' After an exhaustive discussion of the cha- 

 racters of this curious little animal, M. Milne-Edwards 

 comes to the conclusion that it is most nearly related to 

 the members of the following family, and especially to 

 the hamsters, although he found it impossible to unite it 

 with them. In this course he has been followed by other 

 writers. 



" The general construction of the skull is the same as 

 in the Muridse, but from the temporal ridges thin plates 

 are developed, which bend downwards, and articulate 

 with similar plates springing from the malar bones, and 

 thus completely arch over the temporal fossa; after a 

 fashion only met with in certain reptiles, and especially 

 in the Hawksbill Turtle {C/iclone caretta). The whole 

 upper surface of the skull is covered with minute but per- 

 fectly definite granules, arranged with much regularity, 

 and these, which occur in no other mammal, give the 

 skull a very peculiar aspect, such as may be seen in some 

 fishes. As in the Muridae, there are three molars on each 

 side in each jaw, and these are rooted and strongly tuber - 



Hoffmann's Sloth (from lite). 



cular ; the foremost in each series having three and the 

 others each two ridges. Without entering in detail into 

 the peculiarities described at great length by M. Milne- 

 Edwards, we may say that in its general structure, and 

 especially in that of the skeleton, the animal is murine 

 but with a very important distinction, namely, that the 

 collar-bones, which are well developed in the rats and 

 thejr allies, are here reduced, as in the hares and rabbits 

 so as to form only two small bony styles freely suspended 

 among the muscles, and that the first toe in the hind feet, 

 although not very long, is so attached as to be opposite 

 to the rest, thus converting the organ into a prehensile 



hand which the animal uses freely in climbing. The 

 ca?cum is small. 



" In its external characters this animal is as remarkable 

 as in its anatomical structure. In general appearance, as 

 stated by its describer, it has much resemblance to a 

 small opossum, but the bushy tail and the peculiar 

 arrangement of the hair on the body are met with in no 

 marsupials. The head is small ; the general form stout ; 

 the limbs short, and the hind ones not much longer than 

 their fellows ; and the ears are of moderate size and 

 sparingly clothed with hair. The prevailing colour is 

 blackish-brown, but a triangular spot on the forehead, a 



