W. 0. Knight — Notes on the Genus Baptcmodon. 



Art. YII. — Some Notes on the Genus Baptanodon^ with a 

 Descrijption of a New Species ; by Wilbur C. Knight. 



It was many years ago that Marsh described Baptanodon 

 (Sanranodon^), and with the exception of a very short paperf 

 by the same author in which he describes a new species, noth- 

 ing has been written to give lis a better understanding of the 

 peculiar American Ichthyosaur until Charles Gilmore pub- 

 lished some additional and valuable information very recently 

 in Science. 



Yet we do not know very much about this peculiar swim- 

 mer, and a great deal of information is desirable before it will 

 be possible to say with any certainty, whether there is any 

 great difference between Baptanodon and Opthalmosaurus or 

 not. Several paleontologists have already expressed them- 

 selves in the belief that these genera are identical. For a 

 number of years specimens have been accumulating in the col- 

 lection of the University of Wyoming, and from these some 

 valuable points have been secured. From what I know of 

 Baptanodon I am iil favor of retaining the name. In the fol- 

 lowing notes will be found some argument favoring this generic 

 name and showing how that Baptanodon differs from Opthal- 

 mosaurus. 



Front Limb of Baptanodon. — Humerus about one-third 

 the length of the limb, with a stout twisted shaft that is greatly 

 compressed near the distal end. Planes passed through the 

 articulate ends of the humerus stand at an angle of 50°. The 

 head is slightly rounded and is almost identical with Ichthyo- 

 saurus. There are three distal facets ; but they are not of 

 equal size. The facet for the ulna is the largest, the one for 

 the radius next in size, and the one opposite the pisiform is 

 rudimentary, for that bone was held in cartilage and did not 

 articulate with the humerus. These facets are elliptical in 

 form, and those opposite the ulna and radius elongated in the 

 plane of articulation in place of being vertical to it, as they are 

 in Opthalmosaurus. The radius is a subangular bone, with the 

 exterior margin reduced to a thin edge that is nearly straight. 

 It is also larger than the ulna, which is slightly hexagonal in 

 shape. The pisiform is subcircular in form and is the smallest 

 bone of the second segment of the limb. The next segment is 

 composed of four subcircular bones as noted by Marsh, but 

 the succeeding row is composed of only three bones. The 

 largest appears to have been formed by the consolidation of 

 three elements. This might have been considered as an indi- 

 * This Journal, xvii, 85. \ Ibid., xix, 169, 491. 



