1875.] MR. E.R. ALSTON ON THE GENUS ANOMALURUS. 91 
of to the carpus, although the membrane itself springs from the side 
of the wrist*. Thus instead of extending along the free front margin 
of the patagium as in Pteromys and Sciuropterus, it passes diago- 
nally between its folds to the anterior corner. In the one arrange- 
ment the cartilage may be compared to the yard of a lug-sail, in the 
second to the gaff of a sprit-sail. 
Skeleton.—The skeleton of Pel’s Anomalure having been described 
and figured by Gervais and De Blainville, it will be sufficient to 
remark on the points which bear more especially on the affinities of 
the animal. 
The skulls of A. fraseri, A. peli, and A. beecrofti are very much 
alike, though the examination of a series of each would probably 
show constant specific characters. On comparing the skull of 4. 
pelii with that of Pteromys nitidus, the differences already alluded 
to are very striking. The postorbital processes of the frontals are 
rudimentary and almost obselete in the Anomalure, while they are 
largely developed in the Flying Squirrel; on this point, however, 
too much weight should not be laid; for in the African Ground- 
Squirrels (Xerus) and the Chipmunks (Tamias) these processes are 
comparatively small. The other distinctions are all connected with 
the function of mastication. The infraorbital foramen is expanded 
into a large suboval opening in the anterior root of the zygoma, and 
evidently gives passage to a portion of the masseter muscle, as well 
as to the infraorbital branch of the fifth pair of nerves, instead of 
transmitting the nerve only as in Pteromys and the other Sciuride. 
The glenoid cavity is narrower, the articular surface of the condyle 
of the mandible is more sloped outwards; and the bony palate is 
much contracted, convex, and deeply emarginate behind. 
In all other essential characters the skulls appear to me to agree. 
The nasals are narrower in the Anomalure (as they also are in 
Xerus), but of the same general form. The frontals are not more 
contracted (if the postorbital processes be disregarded), and have 
the same median depression. The direction of the temporal ridges 
is the same, as are the position of the foramina of the base of the 
skull, and the size of the incisive foramina. The structure of the 
auditory bull is identical, their interiors being partially divided into 
cells by imperfect bony septa, radiating from the walls towards the 
cochlea: the external meatus is large in both; but in the Anomalure 
its margin is less produced+. The form and proportions of the 
mandible are the same in both animals. 
The other parts cf the skeleton of the Anomalure differ in no 
important point from that of the Flying Squirrel, except the number 
of ribs, of which there are sixteen pairs instead of twelve, and the 
flattening and breadth of the olecranon, to give attachment to the 
cartilage of the flying expansion. The vertebre of A. pelii are :— 
* Temminck was therefore mistaken in stating that the forearm is free in the 
Anomalure (Esquiss. Zool. p. 145). 
t Since the above was written, my friend Mr. A. Doran has called my atten- 
tion to the auditory ossicles of Anomalurus, which arc identical in type with 
those of the true Squirrels. 
