236 MEMOIRS- OF THE CARNEGIE MUSEUM. 
While crania, owing to their fragile nature, have not been recovered in con- 
siderable numbers, mandibles were not uncommon in the quarries. The mandible 
of the mounted specimen No. 1604 was recovered in almost perfect condition, 
having only suffered slight distortion in the region of the symphysis, and in addition 
ten pairs of lower jaws in a more or less complete state of preservation and numer- 
ous single jaws, preserving the lower dentition in perfect order, were found. There 
is therefore no lack of material upon which to form an idea of the form of the 
lower jaw and of the accompanying dentition. 
As has been stated, the skull belonging to the restored skeleton was crushed 
downward. Before mounting the specimen the senior author resolved to effect a 
restoration. Careful measurements of the exposed anterior margins of the ascend- 
ing plate of the maxillary and the contiguous bones when they had been crushed 
down and buckled over each other permitted us to ascertain with approximate 
certainty the height of the nasals above the line of the teeth, and similar measure- 
ments made with great care enabled us to determine the distance of the occipital 
crest above the basi-sphenoid. Having determined in this manner the outline 
of the skull we set to work to make a restoration, the figure of which is given in 
Plate LIII. This restoration is believed to be approximately accurate, and repre- 
sents the general outline as it existed in an uncrushed state. 
The occipital condyles are trihedral in form with the outer surface above and 
below strongly convex, and the inner surfaces which form the lateral walls of the 
foramen magnum deeply excavated. They are sessile upon the paroccipitals and 
at their lower anterior margins project at an elevation of fully five millimeters 
beyond the plane of this lower surface of the foramen magnum, so that there 
appears between them a deep narrow sulcus, far more pronounced than is known 
to the writers in any other of the mammalia except the Rhinocerotide and the 
Equide, where a similar fissure occurs, though not so narrow and therefore rela- 
tively deep. On the posterior surface of the occipital bone there is a well-defined 
ridge, which reaches its greatest development at its junction with the lambdoid 
ridge, where it forms a conspicuous protuberance. On either side of the occipital 
ridge, which rises perpendicularly from above the middle of the foramen magnum, 
are two lateral ridges, which extend upward and outward, terminating on the 
lambdoid ridge at a point on either side about equidistant from the occipital 
protuberance and the junction of the squamosal with the occipital. The lambdoid 
suture appears on the upper surface of the skull and at the middle point lies well 
forward of the ridge which forms the upper posterior boundary of the cranium. 
The paroccipital processes are broad transversely, concave posteriorly at their 
