i MAEINE EEPTILES OF THE OXFORD CLAY. 



examined, nevertheless he still coiisiders that the American and English forms are 

 generically different. Apparently the only reasons for this belief worth considering 

 are : (1) that in Baptanodon the clavicles are fused in the middle line, instead of merely 

 uniting in a close suture ; (2) in the American forms the anterior cervical vertebrse are 

 uniformly biconcave at the ends of their centra, while in the English types the author 

 states that only the middle portion of the centrum is cupped, the concave portion 

 being surrounded by a flattened area; (S) Bapianodon is said to have an additional 

 digit in tlie fore limb. With regard to these differences, taking them in reverse order, 

 it may be said that the number of digits is by no means certain, and, in fact, Knight's 

 figure of the fore paddle of Baptanodon, apparently the only one known in which the 

 bones are in situ, lends no support to the view that six digits were present ; and even 

 if it did so, it is by no means impossible that an extra row of phalanges may not occa- 

 sionally have been present in Ophthalmosaurus. As to the form of the vertebrae, it 

 may be said that in many cases the anterior cervicals of Ophthalmosaurus are biconcave 

 without any broad flattened area round the concavity. Finally, with regard to the 

 fusion of the clavicles in Baptanodon, it would be somewhat remarkable if two bones 

 so closely interlocking as the clavicles of Ophthalmosaurus did not, at least sometimes, 

 fuse in old age, and, as a matter of fact, this seems to have actually happened in 

 some specimens ; in any case, the character does not appear to be of generic value. 

 It seems, therefore, that the English and American species may be regarded as 

 belonging to a single genus, which must be called Ophthalmosaurus, that name having 

 tlie priority, a conclusion already arrived at by E. Fraas * and other writers. The case 

 for this identity is further supported by the fact that the associated invertebrate fauna 

 proves that the beds in which the remains occur were contemporary, and also that 

 there are found in the American deposits remains of a Flesiosaur called by Marshf 

 PanfosaKVUs and clearly identical with Murcenosaurus of the Oxford Clay of England. 

 If further proof of the identity of the American and English genera is needed, i( will 

 be found in comparing the present account of the skeleton of the latter Avith the 

 excellent and detailed account of the former given by Mr. C. W. Gilmore in the papers 

 referred to above. 



Skull. — The skull is represented in the collection by a number of more or less nearly 

 complete examples. The description of the bones of the back of the skull is founded 

 mainly on a series of separate and uncrushed bones of a very large individual (R. 2162), 

 while the account of the facial region is taken from a smaller skull (R. 2180), in which 

 nearly all the bones are preserved separate from one another and only slightly crushed. 

 Only a few bones of the skull of the type specimen are preserved {PL I. figs. 11-15), 

 and to these reference will be made below. 



* '• Weitere Beitrage zur Fauna des Jura von Nordost-Groenland," Meddelelser om Gr^nland, 

 vol. xxi-x. (1904) pt. i. p. 283. 



t « The Eeptilia of the Baptanodon Beds," Amer. Journ. Scl. [3] vol. 1. (1895) p. 406. 



