98 MEMOIRS OF THE CARNEGIE MUSEUM 
roughened surface. The outer lateral surface of this bone is concave from above 
downward (see fig. 5) and roughened for ligamentous attachment to the surrounding 
bones. The inner surface is irregularly concave and roughened down to the inferior 
wedge-like edge. Anteriorly the end resembles that of the posterior view though 
somewhat dished from above downward, and more compressed transversely. It 
was this end of the articular with the surangular that formed the concave articulating 
surface (sq.), for the quadrate. There is no anterior process or elongation of this 
bone and in this respect the articular of Baptanodon 
is much shorter than the corresponding element in 
the Crocodilia. 
In the posterior position of the articular the man- 
ner by which it is retained in the jaw and the part it 
takes in forming the articulation for the quadrate it 
Fig. 4. Internal view of left ar- 
is most nearly approached by the articular of Chelon 
ticular of Baptanodon discus (No. 603). f OK y/ Che Y 
One half natural size. a., anterior end ; maidas. 
p., posterior end ; sq., articulating sur- I have observed several figures of the lower jaw of 
face for quadrate. 
ye eee ee CU OS UUS which show the articular as a small 
bone. One half natural size. d., dorsal triangular bone at the posterior end of the ramus 
surface ; s.g., articulating surface for Jying between the surangular above and the angular 
NL ak Aa case below and visible from a side view. In the speci- 
mens considered here the articular cannot be seen from a lateral view. The 
coranoid (?) apparently overlapped the inner margin above the angular. 
Coranoid (cor.). — Of our knowledge of the extent and nature of the coranoid in 
Baptanodon little can be said at this time. In our specimens it appears as a com- 
paratively thin plate that extends along the inner side of the posterior end of the 
ramus, lapping over the lower border of the articular, thus assisting the angular and 
surangular in holding that element in position. Nothing is known of its extent 
anteriorly. 
Iam pleased to acknowledge my indebtedness to Dr. J. C. Merriam for the 
identification of this element in the material under discussion. On his return from 
Europe last year he examined the skulls and kindly gave me the benefit of his ob- 
servations. 
Dentition. —'The presence of teeth in the American species has long been sus- 
pected by many paleontologists, but until recently” there has been no positive evi- 
dence of their existence. The shallow dental grooves combined with the reduced 
size and undoubtedly loose attachments of the teeth, will fully account for their 
* Gilmore, C. W., ‘‘ Discovery of Teeth in Baptanodon, an Ichthyosaurian from the Jurassic of Wyoming,’’ Scienec, 
N. S., Vol. XVI., No. 414, pp. 913-914, Dec., 1902. 
