Mr. G. R. Waterhouse on the Rodentia. 201 



cola there are some peculiarities which also had considerable 

 weight in my determination to place those genera near to 

 each other, inasmuch as the characters alluded to I have 

 found in no other Rodents. On the other hand, the situation 

 of the ant-orbital opening, and its small size, combined with 

 the number of the teeth (~) and their simple form, ren- 

 der it desirable to raise the Ascomys group to the rank of a 

 subfamily. The genus Castor is likewise somewhat isolated, 

 and may be regarded as a subfamily. Whether these two 

 little sections be an offset, as it were, from the Muridce or the 

 Sciuridae, is difficult at present to determine ; they both want 

 the post-orbital process to the temporal, which runs through 

 the SciuridcB ; but the genus Aplodontia forms a connecting 

 link to a certain extent, having rootless molars, wanting the 

 post-orbital process, but at the same time possessing the small 

 fifth molar in the upper jaw, placed in front of the others, which 

 is found in no other Rodents excepting the Sciuridce. The 

 Aplodontia, moreover, in the form of the lower jaw, evidently 

 links itself with the burrowing Sciuri. With respect to the My- 

 oxida and Gerboidce I have nothing further to add ; they are 

 well-marked sections, and it appears to me their characters 

 cannot better be indicated in a classification than by placing 

 them between the Sciuridce and the Muridce. On one point, 

 however, I cannot quite satisfy myself, and that is the rank 

 of these two sections, — whether they ought to be regarded as 

 families or subfamilies. The former I am of opinion has most 

 claim to be regarded as a family ; the latter will probably 

 merge into the Muridce, and it will then be desirable to regard 

 it as a subfamily, distinguishable by the large size of the ant- 

 orbital opening to the skull, &c. 



A very interesting new rodent, brought from Fernando Po 

 by Mr. Fraser, naturalist to the Niger expedition, and de- 

 scribed by me, under the name Anomalurus Fraseri, at the 

 meeting of the Zoological Society for Sept. 27th, 1842, affords 

 an interesting link, in some of its characters, between the 

 My oxida and the Sciuridce. This animal, — which has the ex- 

 ternal appearance of a Pteromys, a very delicate and soft fur 

 of a sooty colour on the upper parts of the body, freckled 

 with yellow, and whitish beneath, and is remarkable for having 

 on the under side of the basal third of the tail a double lon- 

 gitudinal series of large horny scales, with prominent angles, 

 used by the animal to support itself on the trunks of the trees 

 on which it lives, — has a skull nearly agreeing in general form 

 with the Squirrels, but wanting the post-orbital process, and, 

 what is moreover interesting, has a comparatively large ant- 

 orbital opening, as in the Myoxu The palate is contracted in 



