GILMORE: OSTEOLOGY OF BAPTANODON (MARSH) ntblG 
between the jaws near the end of the snout. Subsequent to this first discovery the 
jaws were partially separated from one another and seven more teeth were found 
scattered at intervals along and between the mandibles. Though no teeth were 
found in the dental grooves of the second specimen No. 878 rudimentary alveolar 
partitions (see P]. VIII.) were present near the front together with a few faint 
sockets at the back of the rostrum. 
The finding of teeth in one specimen (No. 603) and evidence of their existence 
at one time in a second individual (No. 878) led me to believe that dental grooves, 
if not teeth, would be found in the type of the genus Baptanodon if that specimen 
were thoroughly prepared. Only a little preparation was necessary to demonstrate 
the existence of well-developed dental grooves on both upper and lower jaws in 
both types, and just outside of the dental grooves imbedded in the matrix surround- 
ing the rostrum of No. 1952” (B. natans, type of the genus) a small tooth” was 
found. 
The finding of dental grooves and teeth in the types as well as their existence in 
two individuals preserved in the collections of this museum clearly demonstrates the 
fact that American Ichthyopterygians of the Jurassic possessed teeth and were not 
edentulous as originally described by Professor Marsh. Thus the one important 
generic character which has for so long a time separated the American form from 
Ichthyosawrus, and the closely allied European genus Ophthalmosawrus, has been 
shown to be an erroneous determination. 
Among the other distinguishing characters ascribed to the type B. (Sawranodon) 
natans by Marsh, are the number and position of the sclerotic plates of the eye. 
He says: ‘The sclerotic ring is composed of eight plates. . . . These plates are not 
arranged in a nearly flat ring, as in Ichthyosawrus but form the basal segment of an 
elongated cone, as in the eyes of some birds.” The badly crushed condition of the 
skull of No. 1952 makes it impossible for any one to determine with any degree of 
accuracy the precise number of plates composing the sclerotic circle. The right 
orbit, which is the better preserved, contains only two plates with the impressions 
of three others, the intervening space in the ring between the plates and impressions 
being filled with matrix. The “cone-like”’ position of these plates is unmistakably 
produced by crushing. The right orbit of No. 603 shows the sclerotic ring as hay- 
ing been subjected to pressure antero-posteriorly, and here we find the plates assum- 
ing the cone-like arrangement, though it is not so exaggerated as in the former case. 
59 Catalogue number of the Yale Museum. 
51 Gilmore, C. W., ‘‘ Discovery of Dental Grooves and Teeth in the Type of Baptanodon (Sauranodon) Marsh,”’ 
Science, N.S., XVII., No. 436, May 8, 1903, p. 750. 
52 Type of the species, B. discus. 
