104 



NATURAL HISTORY. 



SKULL OF LOPHIOMYS. 



organisation which distinguish it more or less from its fellows ; and in many cases the creatures which 

 are regarded with the most interest by the naturalist are those which seem most to withdraw them- 

 selves from general observation. A single genus, perhaps containing only one or two species, may, by 

 a singular combination of characters, be so completely isolated from all the recognised allied groups 

 that it cannot be placed in any of them, and accordingly a distinct family, possibly even an order, 

 has to be established for its reception. Sometimes subsequent discoveries add to the number of species 



forming the group thus set up, and in this way the prescience 

 of its founder is confirmed. Sometimes the group remains in 

 its original condition, leaving us, according to circumstances, 

 to regard the anomalous creatures of which it is composed 

 either as a special development of their general type, or as the 

 residue of a group which may have presented a greater variety 

 of forms at some past period of the earth's history. 



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 ;* 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 arrange- 

 ments 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. 



The general construction of the skull is the same as in the Muridee, but from the temporal ridges 

 thin plates are developed, which bend downwards, and articulate with similar plates springing from 

 the malar bones, and thus com- 

 pletely arch over the temporal 

 fossae 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 Muridse, 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 impor- 

 tant distinction, namely, that the collar bones, which are well developed in the Rats and their allies, 



* Having the hind feet hand-like. 



LOPHIOMYS. 



