Page:Notes on Osteology of Baptanodon. With a Description of a New Species.pdf/2

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MEMOIRS OF THE CARNEGIE MUSEUM

to make certain alterations and additions to the description and drawings then given, especially those relating to the elements of the skull and lower jaws.

The parts of specimen No. 1441 recovered consist of a skull and lower jaws lacking a median section of the rostrum, the coössified atlas and axis, third and fourth cervicals, besides vertebræ in various stages of preservation from other parts of the vertebral column. With the exception of the proximal end of one humerus, the ulna, and a few paddle bones, all other elements are missing.

The Skull.

The cranium, although subjected to severe pressure, which has somewhat dis-torted the outlines of the skull, appears very similar to those previously described in the paper above mentioned, with the exception that it pertains to a somewhat smaller individual.

The superior view shows the transverse displacement between the anterior end of the postfrontal and the posterior end of the nasal, and, as breaks occur in identi-cally the same place, and take the same transverse direction in two other crania (Nos. 603 and 878) in the collections of the Carnegie Museum, the writer now as-sumes this displacement as following the line of suture, and in the corrected draw-ing (See Plate XXXVII, Fig. 1), they are indicated as absolutely determined. The suture separating the premaxillary at the anterior third of the rostrum is plainly shown in this specimen. Another point of interest is the wide prefrontal developed in this individual.

Viewed laterally this skull sheds new light on the posterior termination of the premaxillary. In Baptanodon the posterior end of the premaxillary is somewhat forked as in many forms of the Ichthyosauria. The lower posterior branch extends back under the nares, laps over and hides from a lateral view most of the anterior prolongation of the maxillary. (See Plate XXXVI.) The longitudinal channel along the side of both the premaxillaries and dentaries, just above and below the dental grooves (See Fig. 1 has many more nerve pits for the entrance of nerves to the teeth than was indicated in the first restoration of the skull of Baptanodon. A pineal foramen appears to be present and occupying essentially the same position as in the other skulls in this museum. The posterior part of the skull is so badly dis-arranged that nothing of importance is shown.

The other views of the skull show nothing new, and, as the other elements have been fully described in a previous paper, it is unnecessary to repeat the description here.