Page:Notes on Osteology of Baptanodon. With a Description of a New Species.pdf/12

The anterior border of the parts preserved is slightly rounded, but, as it approaches the articular end it widens into flattened oblique surfaces which look forward and upward and probably represent the points of attachment for the ligaments which held the clavicles in position. (See Pl. XXXVIII., Fig. 1.) The ventral surface of the scapulæ antero-posteriorly at the expanded articular ends is somewhat concave. Between the point of attachment for the clavicle and the articulation with the coracoid the internal border is especially compressed and remains free.

The clavicles and interclavicular bones were not found with this specimen.

Measurements.

No. 919. Greatest width of coracoids, transversely....................................................................................................................................................................................................................................................430 mm.

" 919. " length of articular surface for scapula....................................................................................................................................................................................................................................................83 "

" 919. " " of straight external border....................................................................................................................................................................................................................................................110 "

" 919. " width of scapulæ, antero-posteriorly....................................................................................................................................................................................................................................................175 "

" 919. " length of glenoid articular face....................................................................................................................................................................................................................................................60 "

Comments on Recent Literature.

In discussing the age of the Baptanodon Beds Dr. S. W. Williston^[1] speaks of the relationship of Baptanodon and Ophtalmosaurus and makes the statement that the two species of Ophtalmosaurus are probably not congeneric and it is also apparently quite true that Baptanodon seems to be as closely allied to the Cretaceous as to the Jurassic species. In a previous paper^[2] I have shown that O. icenicus (the Jurassic form) and Baptanodon are very closely allied, while O. cantabrigiensis is not similar in any respect.

The discovery the past season (1905) by Mr. W. H. Reed of an Ichthyosaurian in the Benton Cretaceous is of considerable interest as showing the occurrence in North America of this group at a much later period than hitherto supposed.

Dr. J. C. Merriam, who has examined the fragmentary specimen collected by Reed, says:^[3] " The centrum is very thin antero-posteriorly and in this respect some-what resembles the corresponding centra in Baptanodon discus. . . . When more material is available it will be interesting to learn. whether this form really repre-sents a true- Ichthyosaurus or possibly a more highly specialized form of Baptanodon than those we know from the Baptanodon beds. Should it be Baptanodon, it will

1. Williston, S. W., " Hallopus, Baptanodon and Atlantosanrus Beds of Marsh," Jour. of Geology, Vol. XIII., No. 4, May-June, 1905.
2. Gilmore; C. W., "Osteology of Baptanodon," Memoirs of the Carnegie Museum, Vol. II., No. 2, August, 1905.
3. Merriam, J. C., "The Occurrence of Ichthyosaur-like Remains in the Upper Cretaceous of Wyoming," Science, N. 8., Vol. XXII., No. 568, pp. 640-641, November 17, 1905.