182 MEMOIRS OF THE CARNEGIE MUSEUM 
crest, presenting a comparatively plane surface. The transverse diameter of this 
surface is twice that of the vertical. The mastoid bulle are only slightly in- 
flated. The supraoccipital cannot be outlined by the suture, but is undoubtedly 
very large, to judge from the broad aspect of the skull in this region. The basi- 
occipital is not excavated as in the beaver; it is somewhat triangular in shape, 
with two small perforations, one on each side of the median line opposite the 
posterior part of the tympanic bulle. Postero-laterally from these perforations 
are the rather large condylar foramina. The occipital condyles are of moderate size, 
not very greatly separated inferiorly by the deep triangular notch ; and they are 
farther separated from the tympanic bulla than in Steneofiber fossor. The foramen 
magnum is of large size and subtriangular in shape. The mastoid process is of 
medium size, and has a unique outward and horizontal position, similar to that in 
Aplodontia, but is more rounded. ‘The long, constricted tube of the auditory bulla 
is supported by the mastoid process nearly to its outer portion — the external audi- 
tory meatus. The latter opening is broken away in our specimen, but was perhaps 
not of great size to judge from the greatly constricted tube. The tympanic bulla is 
much inflated, chiefly laterally and antero-posteriorly ; it is depressed vertically, and 
takes up a considerable area of the basicranial surface. The shape of the bulla is 
flask-like, with an unusually long and much more constricted neck than in Aplo- 
dontia. The genus Hntoptychus from the John Day Miocene has the constricted 
neck of the bulla; but the general features of the skull in Huhapsis are entirely dif- 
ferent from it, and bear a more general resemblance to Steneofiber. 
The Squamosal has a considerable posterior process, which unites with the base 
of the mastoid process from which the lambdoid crest takes its origin. In front of 
this process, and immediately behind the zygomatic process of the squamosal is a 
deep rounded emargination (the postglenoid notch), similar to that in Steneofiber, 
Entoptychus, and the recent genus Aplodontia and the Geomyidx. In Huhapsis platyceps 
the zygomatic process of the squamosal is of small size and rather short ; the jugal 
and zygomatic process of the maxillary furnishing the greater part of the arch. 
There is an obtuse, round, postorbital swelling, from which continues latero- 
inferiorly a sinuous ridge, which is continuous with the anterior margin of the 
zygomatic process. ‘The glenoid cavity is not as distinctly formed as in Fiber zi- 
bethicus, and indicates a considerarable lateral motion of the mandible. The anterior 
border of the squamosal cannot be accurately determined, since the suture is oblit- 
erated at the posterior margin of the orbit. The parieto-squamosal suture is much 
lower down on the side of the skull than in Steneofiber fossor. 
In the region of the sphenoid bones the skull is damaged. The basisphenoid 
