GILMORE : NOTES ON OSTEOLOGY OF BAPTANODON 329 
birds. It may prove to be the case that these bony plates curve in on the back of 
the eye similar to the cartilaginous protection of the eyes in some of the whales. 
The surface markings of the sclerotic plates have been fully described in a pre- 
vious paper. 
DENTITION. 
No. 1441 gives but little information regarding the teeth of this form. Only one 
tooth was found intact, this being in position near the anterior end of the rostrum. 
(See Fig. 4.) 
This tooth measures 13 mm. in length and isa good example of the anterior 
teeth as known in two other individuals of this group. There is no swelling at the 
base, as may be observed in the teeth of some of the Ichthyosaurs. This tooth is 
circular in cross-section, ending in a sub-acute apex, the top being covered with 
pace ues 
a 
a : Fie. 5. Cross-section 
near the middle of the snout 
2 of Baptanodon natans (No. 
Fia. 4. Lateral view of a section of the anterior part of 1441). One halé natural 
the rostrum of Baptanodon natans (No. 1441). One half nat- size. d., dentary; d.g., 
ural size. a., anterior end; d., dentary ; p., posterior end ; dental grooves ; pmz., pre- 
pmx., premaxillary. maxillary. 
enamel without striation. In the latter respect the tooth appears very similar to 
the single tooth known in the type of Baptanodon natans. There are parts of other 
teeth preserved which are more slender and pointed than the one just described, but 
their enameled surfaces are perfectly smooth. The presence posteriorly of faint alve- 
olar partitions indicates the position of other teeth. Because of the small size of 
this individual and the apparent similarity of the teeth I refer this specimen to B. 
natans. Fig. 5 shows a cross-section of the rostrum somewhat anterior to the sym- 
physis and gives a good idea of the depth and shape of the dental grooves in this 
part of the snout. 
VERTEBR&.” 
The atlas, axis, third, and fourth cervicals were found in the matrix but little 
removed from their normal position at the back of the skull and still in contact 
5Mr. W. H. Reed writes me that there are fifty consecutive vertebree in the caudal series of specimen ‘‘T’’ in the 
collection of the University of Wyoming, instead of forty-six as published by Knight and quoted by me in a later paper. 
