0. C. Marsh—Structure of Mosasauroid Reptiles. 449 
Harger, of the Yale exploring party, who discovered a quadrate 
bone of Lestosaurus latefrons Marsh, in place, and firmly united 
to the suspensorium. Another specimen in the 
is equally conclusive. The natural position of the quadrate, 
therefore, in the Pythonomorpha is with the great ala external. 
This clears up, at once, several difficulties in regard to the mo- 
tion of the jaws, which could not be satisfactorily explained 
when the quadrates were reversed. is discovery of its 
true position necessitates a change of terms used in deseribin 
this bone, and those proposed by Prof. Cope may be amend 
as follows:—The “external angle” may be called the internal 
angle; the “external ridge,” the internal ridge ; and the “ distal- 
external longitudinal ridge” may be termed the internal longi- 
tudinal ridge. 
genus (Z. felix Marsh), the entire stapes, apparently, was 
1] i each case the bone 
8. Discovery of the Columella. No evidence of the existence 
of this bone in the skull of any Mosasauroid reptile has hitherto 
been adduced, and Prof. Cope asserts that it im not exist In 
the group.* In removing th 
skull of Lestosaurus felix, which had the stapes preserved, the 
Writer found a slender cylindrical bone adhering to the basi- 
what compressed throughout, slightly sigmoid, and has both ends 
ghtly sigmoi t 
moderately expanded. The tose larger, extremity has a 
f its gre 
in * Synopsis of Extinct Batrachia, etc., p. 176. 
- Jour. Sct.—Turep Serres, VoL. III, No. 18.—June, 1872. 
29 
