524 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
sutures persist plainly visible in adult life; and all the bones are remarkably 
thin and papery. 
Viewed in profile, the skull shows notable features. The highest point 
is over the orbits, where the frontal and parietals are seen to be swollen; 
thence the superior outline sweeps gently down to the occiput, and in the 
other direction proceeds in a nearly straight—if anything, slightly concave— 
line to the tip of the snout. The great projection of the nasals beyond the 
intermaxillaries is well shown. The incisors in profile are seen to curve far 
backward as well as downward. The palatal outline is nearly straight, and 
declivous from before backward. Behind the palate, a small pterygoid hook 
is seen; but beyond this the whole outline is the inflated portions of the tem- 
poral bone hiding everything else. On the side of the rostrum midway, there 
is a large circular foramen, low down, but little above the palatal level; this 
is the orifice corresponding to the ‘‘anteorbital” foramen, here singularly dis- 
placed. From its fellow of the opposite side, it is only separated by a very 
thin vertical septum, apparently ethmoidal. This delicate partition, being 
often broken through in prepared skulls, has occasioned the statement of the. 
intercommunication of the two foramina. But I find the septum complete 
and intact in some specimens, and although a vacuity may very possibly nat- 
urally occur, such does not appear to be the rule. The orbit appears as a 
subcircular fossa, largely roofed over in front by the thin expanded zygomatic 
plate of the maxillary, and bounded below by the malar. Independently of 
its laminar maxillary portion, the zygoma is a slender, straight thread down 
to the palatal level, and abutting behind against the tympanic. The actual 
suture is squamosal, of course, but there is a curious appearance of connection 
with one of the otic bones. In the general inflation of the posterior portion 
of the skull appears the large orifice of the meatus auditorius—a simple cir- 
cular opening in the bullous mass. 
Viewed from below, the general contour is substantially the same as that 
already noted from above; but many special parts claim attention. So great 
is the backward obliquity of the incisors that their faces show in this view 
with comparatively little foreshortening. The incisive foramina are a pair of 
contracted slits midway between the incisors and molars. The palatal sur- 
face in advance of the molars is much compressed; that between these teeth 
is broader and quite flat; its width posteriorly is little less than its length; 
it contracts somewhat anteriorly, where it is marked by a median ridge con- 
