x 
454 0. C. Marsh—Structure of Mosasauroid Reptiles. 
Number of Cervical Vertebre. In all the genera examined 
during the present investigation, the skull was supported on a 
very short neck, much shorter, in fact, than any species of the 
group has been supposed to possess. Prof. Huxley, in the work 
already cited (p. 224), places the Mosasauria with the Reptilia 
aving more than nine cervical vertebra ; and Prof. Cope states 
(Synopsis, p. 218) that in Chdastes propython there are ten cer- 
vical vertebre with articulated hypapophyses. In the Yale 
useum are numerous series of cervical vertebra of Lestosaurus, 
all apparently complete, and several of them known to be 80, 
as they were found in position. None of these series have over 
four vertebrae with articular faces for hypapophyses behind the 
axis, and following these one, or sometimes two, with a tubercle 
more or less developed. In Hdestosaurus, judging from several 
series of cervicals apparently complete, there were probably but 
ve vertebre with free hypapophyses, in addition to the atlas 
and axis, and, posterior to these, two or three with small rugose 
tubercles. The same number was observed in a specimen of 
inosaurus. It is evident, therefore, that the neck in this 
group was unusually short, resembling very nearly, among 
swimming Saurians, that of Jchthyosawrus. 
New Genera and Species. 
In a catalogue, recently published, Prof. Cope has given 4 
complete and instructive list of the species of Pythonomorpha 
now known from the Cretaceous deposits of Kansas.* these 
species are arranged under various generic names, which do 
not, in all cases, meet the requirements of our present knowl 
edge of these reptiles, especially in view of the hight thrown o 
the subject by the very large collections made in that region by 
the two expeditions from Yale College. An attempt 18 “— 
fore made below to define more closely the generi¢ relations 
the groups best represented in the West. The material for 4 
similar definition of some of the rarer forms, as well as t e 
from the Eastern Cretaceous beds, has not yet been broug 
together. 
Lestosaurus,t gen. nov. 
United premaxillari short obtuse 
muzzle, that extends little if any in front of the premaxillary 
ings American Philosophical Society, vol. xii, Dee., 1871. 
* Proceedi 
+ Agoric, pirate, and cavpoc, lizard. 
much 
