450 0. C. Marsh—Structure of Mosasauroid Reptiles. 
pointed tubercle at the posterior external angle. tosau- 
rus, the jugal has a less complicated union with the post-frontal, 
and is throughout a more slender bone. This arch is apparently 
well developed also in Rhinosaurus. : 
6. Pterotic bone. Among other new points brought to light 
during the present investigation of the cranium of the Pythone 
morpha, may be mentioned the discovery, in Hdestosaurus, 4 
distinct ossification at the distal end of the suspensorium, whi! 
is evidently the element called the pterotic by Huxley. Itis 4 
small oval bone, which is attached to the opisthotic, and yr 
on the superior surface of the quadrate. In several of ied 
genera of this group, the cartilaginous wall which exten i 
from the quadrate to the base of the skull was so much ossifi 
that large sheets of this membrane are frequently found La 
served, adhering to the quadrate, or the lower part of the sk 
Laie ee ae 
7. Anterior Limbs. recently the nature 0 
r 8. very y and in Our 
prove that these limbs were es in the pepe fe 
estosaurus simus Marsh, which shows at a rigid 
of the scapular arch and the corresponding limb. This ee 
oe with other important parts of the same skeleton, exact 
ound, by the writer, with the various bones almost in the 
* Huxley, Anatomy of Vertebrated Animals, p. 230, 1871. 
