1869.1 251 [Cope. 



PYTHONOMORPHA. 



At present I propose to notice the fifth and sixth results of these 

 investigations. 



The genus Mosasaurus, since the discovery of the large specimen in 

 the St. Peter's Mount at Maestricht, has been a subject of discussion 

 by many palaeontologists, and always to the writer, with unsatisfac- 

 tory results. While Faujas held it to be a crocodile, Camper and 

 Cuvier regarded it as a lacertiliaii, and placed it near the Monitors. 

 In the latter relation it has been allowed to remain by Goldfuss and 

 Owen, who have since written upon it, and so it continues to be re- 

 garded by all palaeontologists of the present day, who have expressed 

 an opinion on the subject. 



I hope, however, to be able to demonstrate, by the light of ney 

 material recently discovered, that the Mosasauridae and Clidastid® 

 constitute a peculiar order of reptiles, which possess many of the 

 characters of serpents, with some of Lacertilia, and others of the 

 Sauropterygia. The reason why, as I conceive, this genus and its 

 alUes have been so little understood, has been a lack of analysis of 

 the structure of portions of the ei-anium little known, as well as of 

 portions better known; and the lack of certainty as to the structure 

 of the limbs. 



With reference to the latter, Cuvier says that very few bones of 

 the extremities of Mosasaurus have been found, and their rarity was 

 such that, for a moment, he was led to doubt whether the animal pos- 

 sessed limbs. He states that he was soon undeceived by recognizing 

 a bone of the pelvis which certainly belonged to Mosasaurus. The 

 bone considered to be a pubis, resembhng that of the Monitor, is 

 figured in the Ossemens Fossiles. Cuvier further says, that among 

 some fossils from Seichem, he detected a scapula resembling that of 

 the Monitor, and subsequently received drawings from Maestricht of 

 a clavicle resembling that of a common lizard, and also a coracoid 

 bone. From the specimens and figures, Cuvier supposes the shoulder 

 of the Mosasaurus to have exhibited a close resemblance to that of 

 the lizards. After remarking that he had been unable to procure 

 any long bones of the limbs of Mosasaurus, he expresses his views in 

 regard to certain figures of bones, represented by Faujas-Saint-Foud 

 and Camper, reproduced in the Ossemens Fossiles. In regard to the 

 figure of a portion of an ulna, Cuvier says that if the bone belonged 

 to Mosasaurus, it would indicate the exti-emities to have been moder- 

 ately elevated. But, he continues, the bones of the feet, so for as 



