60 
ICHTHYOSAURIA FROM THE 
Case. Shelf. No. 
X 6 5 —6 trapezoidal in inferior outline and in an¬ 
terior outline; and from behind subquad¬ 
rate, sending off inferior lateral wings in 
front. Tlie small cup-shaped facet for the 
basi-occipital makes an angle of 45 degrees 
with the triangular palatal surface of the 
specimen. The inferior aspect shows im¬ 
pressions at the sides, for the pterygoid 
bones which converged behind and appear 
to have nearly or quite surrounded the 
posterior outlet of the large sub-cylindrical 
channel which passes obliquely backward 
and downward from the base of the sella- 
tursica. This tube is described by Prof. 
Owen as the Eustachian tube; it appears 
to be the perforation for the carotids. 
Anteriorly the straight palatal borders 
extend but little in front of the cranial 
border. The rostrum which supported the 
pre-splienoid is broken away. 
b 7 —11 Examples of the basi-sphenoid bone, of which 
b. 7 and 6.11 are well preserved. They are 
all smaller than b . 6 , and indicate a well- 
marked distinct species. In 6.8 the quad¬ 
rate articular facet for the basi-occipital, 
which is concave from side to side, makes 
an angle almost of 90° with the slightly 
convex inferior surface. This surface is 
made slightly sub-pentagonal by a short 
mesial rostrum in front. Between this 
rostrum and the perforation for the carotids 
is the ovoid articular facet for the (elon¬ 
gated) pre-sphenoid. The cranial surface 
is rough, suggestive of a cartilaginous box 
for the brain. The pterygoid bones do 
not impress the inferior palatal surface. 
The anterior aspect is convex from side to 
side and concave from above downward. 
