162 O. C. Marsh—New Family of Dimosaurs. 
On the median line, directly over the cerebral cavity of the 
brain, the type specimen of Diplodocus has also a fontanelle 
in the parietals. This, however, may be merely an individual 
peculiarity. 
ormed almost wholly of the basi-occipital, the exoccipitals en- 
tering but slightly or not at all into its composition. 1 he bast 
occipital processes are large and rugose. The paroccipital pro- 
cesses are stout, and somewhat expanded at their extremities, 
for union with the quadrates. : 
The parietal bones are small, and mainly composed of the 
arched processes which join the squamosals. There is no tue 
parietal foramen, but in the skull here figured (Plate Ill) 
there is the small unossified tract mentioned above. In one 
specimen of Morosaurus, a similar opening has been observed, 
ut in other Suuropoda, the parietal bones, even if thin, are 
complete. The suture between the parietals and frontal bones — 
is obliterated, in the present skull, and the union is firm m all | 
. the specimens observed. me 
The frontal bones in Diplodocus are more expanded trans — 
versely than in the other Sauwropoda. They are thin along the 
median portion, but quite thick over the orbits. ; 
e nasal bones are short and wide, and the suture between 
them and the frontals is distinct. They form the posterlol 
boundary of the large nasal opening, and also send forward ® — 
process to meet the ascending branch of the maxillary, thus 
forming in part the lateral border of the same aperture. d & 
The nasal opening is very large, subcordate in outline, am 
is partially divided in front by slender posterior processes“ 
the premaxillaries. It is situated at the apex of the skull, be x 
tween the orbits, and very near the cavity for the olfactory — 
lobes of the brain. a 
The premaxillaries are narrow below, and with the ascent 
gate. Along the media? . 
functional teeth. 
The maxillaries are very largely developed, more so thane" 
most other known reptiles. The dentigerous portion 18 Vo! 
high, and slopes inward. The ascending process is very“ & 
thin and flattened, inclosing near its base’an oval foramen; ®” 
