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 is a 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
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| Fig. 5. Cross—section near the middle of the snout of Baptanodon natans (No. 1441). One half natural size d., dentary ; d.g., dental grooves ; pmx., premaxillary. | Fig. 4. Lateral view of a section of the anterior part of the rostrum of Baptanodon natans (No. 1441). One half natural size a., anterior end ; d., dentary ; d.g., dental grooves ; pmx., premaxillary. |
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 alveolar 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.
Vertebræ[1]
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
- ↑ Mr. W. H. Reed writes me that there are fifty consecutive vertebræ 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.
