240 MEMOIRS OF THE CARNEGIE MUSEUM 
tion there were nine teeth in the maxillaries and ten in the dentaries. In the speci- 
men preserved in the American Museum of Natural History the number of teeth in 
the dentaries corresponds with the number given by Professor Marsh, but in the 
right maxillary in this specimen there are ten teeth while in the left maxillary 
there are eleven. The successional teeth are numerous, and nature provided the 
animal with the means of replacing a tooth almost as soon as it was lost. The 
arrangement of the teeth is rake-like, without distinct provision either for cutting 
or grinding, and suggests to the mind that they were employed for gathering soft 
succulent vegetation, which may have grown in masses upon the rocks of the shore. 
The feeding habits of the creature are, of course, unknown, but such teeth are appar- 
ently better adapted to raking and tearing off soft masses of clinging alge than any 
forms of vegetable food which now exist in the waters of the world. 
OPENINGS IN THE SKULL. 
Larger Foramina. — The larger openings in the skull are the foramen magnum, 
the posttemporal fossee, the supratemporal fossee, the infratemporal vacuities, the 
orbital cavities, the narial opening, the preorbital vacuities, the large openings in 
the maxillaries, which I have designated as the mesial foramina of the maxillaries, 
and the foramina at the point of union of the premaxillaries and the long bones re- 
garded by Professor Marsh as posterior processes of the premaxillaries. 
The Foramen Magnum (Figs. 4 and 6 and Plates XXV., XXVI., and XX VII.). — 
The foramen magnum is bounded below by the basioccipital, and on either side and 
above by the exoccipitals. In specimen $82, where there has been no crushing 
whatever in this region, the foramen is shown to be approximately ovoid in outline, 
with the longer axis perpendicular, the upper end decidedly narrower than the 
lower end of the opening. (See Fig. 4.) 
The Posttemporal Fosse (Figs. 4, 6, 8, and 10, and Plates XXV. and XXVI).— 
These are paired, one on either side of the exoccipitals. Each opening is bounded 
on its lower margin by the excavated margin of the paroccipital process of the ex- 
occipital bones, and is bounded above by the lower margin of the squamosal. The 
upper end of the opening, when viewed from behind, is bifid, because of the intru- 
sion into it of a short, blunt process which is sent forth downwardly and out- 
wardly from the upper margin of the exoccipitals where they articulate with the 
syuamosal. The lower extremity of the opening is closed by the proximal end of 
the quadrate. 
The Supratemporal Fosse (Figs. 8-6 and 10 and Plates XXIJI.-X X VIII.). — The 
supratemporal fossa is oval in form, and is directed upward and outward. Its walls 
