The latter is perhaps the case with the curious little Rodent which alone forms the present family, of which its original describer, M. Alphonse Milne-Edwards, writes as follows:--“In its general aspect it somewhat resembles certain Opossums, and like these it is pedimanous;[52] but these are the only analogies it presents to the Marsupials, and in its dental system, as also in the rest of its organisation, we easily see that it belongs to the order Rodentia. It differs, however, from all the members of this group by characters of considerable importance; I may even say that, by some peculiarities 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 characters 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. [Illustration: LOPHIOMYS.] The general construction of the skull is the same as in the Muridæ, 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 fossæ after a fashion only met with in certain reptiles, and especially in the Hawksbill Turtle (_Chelone caretta_). The whole upper surface of the skull is covered with minute but perfectly 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 Muridæ, there are three molars on each side in each jaw, and these are rooted and strongly tubercular; 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 their 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 cæcum is small.