SQUAMATA 



159 



present in lower part of the basioccipital. Mandible strong, upper edge 

 concave, coronoid process prominent. Coracoid non-emarginate ; chevrons 

 loosely articulated. Brown Phosphate Chalk ; Belgium. 



Brachysaurus, Williston. Frontal large and broad ; no median basioccipital 

 canal. Suprastapedial process of quadrate coossified with the infrastapedial. 

 No zygosphenes ; chevrons fused with their centra. Possibly identical with 

 preceding genus. Ft. Pierre Cretaceous ; South Dakota. 



Phospliorosaurus, Dollo. Imperfectly known. Frontal very narrow, with 

 nearly parallel sides, and taking part in the superior border of the orbit. 

 Parietal small ; its exposed surface triangular, and with very large foramen 

 at its front margin. Suprastapedial process much elongated and united with 

 the infrastapedial, enclosing an elongated meatal opening. Tympanic cavity 

 extended and shallow. Upper Cretaceous ; Belgium. 



Taniwhasaurus, Hector. Allied to Platecarpus. Cretaceous ; New 

 Zealand. 



Sub-Family C. Mosasaurinae. Williston. 



Hind limb tetradadyle. Trunk elongated, tail much dilated distally. Pox- 

 maxillae forming a short and oUusely conical rostrum. Prefrontals more or less 

 dilated into a horizo-ntal plate posteriorly. Quadrate small, with moderate-sized 

 suprastapedial process. Coronoid large, articidating with the splenicd on the inner 

 side. Humerus with strong radial process at distal end. Carpus and tarsus com- 

 pletely ossified ; not more than six phalanges in any of the digits. Zygosphenes rudi- 

 mentary or functional, chevrons fused with their centra. 



Clidastes, Cope (Mesfosaurus, Marsh), (Figs. 242, 4, 6, 7, 251). Skull 0-4 

 to 0'7 m. long ; slender, 

 tapering, depressed. 

 Frontal not emarginate 

 posteriorly in the 

 median line. Parietal 

 foramen entirely within 

 the parietal plate. 

 Teeth facetted on outer 

 side, and smooth on the 

 inner or on both faces. 

 Dentary with about 

 seventeen teeth, maxilla 

 fifteen, pterygoid 

 twelve to fifteen. 

 Zygosphenes func- 

 tional ; chevrons long. 

 Neural spines elevated 

 in posterior half of the tail, suggesting presence of a caudal fin. Upper 

 Cretaceous ; Kansas, Alabama, and New Jersey. 



Mosasaurus, Conyb. (Leiodon, Owen ; Pterycollasaurus, Dollo), (Figs. 243, 

 252). Skull attaining a length of 1-2 m., and total length of about 12 m. 

 Distinguished from Clidastes chiefly by absence of a zygosphene-zygantrum 

 arrangement. There are more than 130 vertebrae in the column, of which 

 46 are precaudal. The massive upper jaws are armed with about foiirteen 



Clidastes propython, Cope. Upper Cretaceous ; Uiiiontown, Alabama. 

 Skull, superior and lateral aspects, i/n (after Cope). 



