Williston.] Mosasaurs. 177 



Hainosaurus. 



UainosaiD'us Dollo, Premiere Note sur le Hainosaure, mosasaurien nou- 

 veau de la craie brune phosphatee de Mesvin-Cipley, Ball. Mus. Roy. Hist. 

 Nat. Belg., 1885, n, p. 297. 



Rostrum much prolonged in front of the teeth. Suprastapedial 

 process of quadrate short. Frontal broad, the prefrontal and 

 postfrontal touching each other. Carpals reduced in number. 

 Typical species, Hainosaurus bernardi Dollo, loc. cit. 



This genus is very closely allied to Tylosaurus. The phalan- 

 ges of the front feet are not as numerous, and the paddle is 

 relatively larger. There are, apparently, more numerous dorso- 

 lumbar vertebrae. Like Tylosaurus, it includes some of the 

 largest species of the Mosasaurs. 



PLATECARPIN^E. 



Platecarpince Williston, Kans. Univ. Quart., vn, A, 181, 1897. 



Hind limbs functionally pentedactylate. Trunk short ; the 

 tail proportionally long, not dilated distally. Carpus and 

 tarsus imperfectly ossified. Vertebrae with rudimentary or 

 functional (?) zygosphene. Premaxillary not projecting be- 

 yond the teeth, very obtuse. Quadrate large, with a long 

 suprastapedial process, not united to infrastapedial process. 



Platecarpus. 



Holcodus Gibbes, Smiths. Contr., n, p. 9, 1850. 



Platecarpus Cope, Proc. Bost. Soc. Nat. Hist., xn, 1869, p. 264. 



Lestnsaurus Marsh, Amer. Journ. Sci., June, 1872. 



Medium-sized Mosasaurs. Premaxillary short and obtuse, 

 projecting very slightly beyond the teeth. Teeth slender, and 

 recurved, faceted upon the outer side and striate on the inner. 

 Nares much dilated anteriorly, situated forward. Frontal 

 emarginated in the middle behind ; pineal foramen large, situ- 

 ated near the frontal suture. Facial surface of parietal small, 

 triangular in shape, the apex not extending beyond the middle 

 of the bone. Prosquamosal with a dilated wing-like process 

 above. Quadrate large, with a large suprastapedial process, 

 reaching below the middle of the bone. Expanded portion of 

 palatine short. Coronoid short and not prominent. Zygo- 



