—~™ 
.deeply excavated, angular cavity, 
Apr.1903. NortH AMERICAN PLESIOSAURS—WILLISTON. 27 
for the pituitary, a narrow roof under the parietal, an open vacuity 
posteriorly in the supraoccipitals, and with a relatively large otic 
capsule. The exoccipita/s unite obliquely with the basioccipital, tak- 
ing no part in the formation of the condyle. The paroccipital pro- 
cesses are small and slender, and there is no indication of a distinct 
ossification. They are dilated slightly at the extremity, where they 
abut against the upper part of the quadrate. They are directed down- 
ward and outward, the distal extremity reaching a level below the 
top of the occipital condyle. The occipital foramen is transversely 
oval, if the upper end is assumed to be near the top of the exocci- 
pitals, which show a slight angularity at the place of their union with 
the separated supraoccipitals. | At . 
the upper posterior extremity of 
each exoccipital there is a small, 
excavated almost wholly from the 
exoccipital, its upper border only 
touching the posterior angle of the 
supraoccipital. Itsexcavated sur- 
face is smooth and sharply angu- 
lar, looking upward and inward. 
This surface probably corresponds 
to the smooth tendinous surface 

seen on the outerangle of the supra- Fic. 3. 
occipital, extending slightly on the Dolichorhynchofs osborni. Occipital view of 
- skull. x %. Pa., parietal; sg., squamosal; g., 
Bee amincenmole ot the exocci-. 2. th tO BaTiO Sd Sauamosa’s: @ 
y ‘ ‘ quadrate; so., supraoccipital; eo0., exoccipital; 
pital, in the crocodile. At the ft., pterygoid; oc., occipital condyle; Go., basi- 
posterior part, the exoccipitals occipita 
approach each other rather closely, 
leaving about four millimeters of basioccipital space in the circumfer- 
ence of the foramen magnum. Anteriorly, however, the two bones 
diverge rather widely, terminating a little posterior to the suture 
separating the basioccipital from the basisphenoid. On the inner 
side, back of the middle of the bone, and a third of the distance above 
the sutural margin, is the large oval foramen for the vagus, opening 
exteriorly below the middle of the moderately expanded paroccipital 
process. The smaller foramen for the hypoglossal is situated mid- 
way between this and the posterior margin, and nearer to the sutural 
surface ; it opens near the vagal orifice. The sutural surface for the 
supraoccipital is flat and broadly triangular, pierced near its middle 
by a small foramen leading into the posterior semicircular canal in 
the supraoccipital, the floor of which is seen on this surface, leading 
