138 



teeth. There are two anterior dorsals, three lumbars, and one caudal. The 

 articular faces of the caudals are broad vertical ovals. They increase in 

 width on the lumbars till, on the last of these, they assume the subpentagonal 

 form characteristic of many species, and which is still more marked on the 

 caudal. The centrum of the anterior dorsal is much compressed; interiorly, 

 slightly concave longitudinally, regularly and prominently convex transversely. 

 Conversely, the rims of the cup and ball are. strongly expanded; the latter 

 with surrounding groove. The diapophyses of the lumbars are of consider- 

 able length, exceeding, in this respect, those of Mosasaurus we possess where 

 these parts are preserved. On the median of the lumbars, the inferior sur- 

 face of the centrum first becomes truncate or plane, and separated from that 

 below the diapophyses, which become slightly concave. The expansion of 

 the ball becomes more abrupt and striking on these vertebras. The caudal 

 is a little more compressed than the lumbars, and presents the character of 

 coossified chevron-bones. These are slender and longitudinally grooved. 



A single pterygoid tooth was found in the matrix on one of the dorsals 

 The basis is short and much swollen ; the crown curved, acute, a little com- 

 pressed, and with an obtuse cutting-edge posteriorly. 



Measurements. 



M. 



Auterior dorsal, length of the cunt rum '. 0. 0003 



Anterior dorsal, depth of the articular hall 0. 038 



Anterior dorsal, width of the articular ball 0.038 



Anterior dorsal, diameter behind the diapophyses 0. 029 



Anterior dorsal, depth of the articular face for the rib 0.002 



Lumbar, length of the centrum 0. 000 



Lumbar, depth of the ball 0.037 



Lumbar, width 0.030 



Lumbar, length of the remnant of the diapophysis 0.046 



Lumbar No. 2, length of the centrum 0.055 



Lumbar No. 2, width of the zygosphen 0. 0182 



Caudal, length of the centrum 0.041 



Caudal, depth of the cup 0.040 



Caudal, width of the cup 0.040 



Caudal, wid Hi of the basis of the diapophysis 0.0215 



Caudal, width between the chevron rami 0. Oily 



Pterygoid tooth, height of the crown , 0.0125 



Pterygoid tooth, diameter of the pedestal 0.013 



This species was found by Professor Mudge near the locality of the 

 Platecarpus mudgei, six miles south of Sheridan, Kansas. 



Tt is only necessary to compare (his species with G. intermedins, Leidy, 

 a- the C iguanavus and G. propython have depressed vertebral centra. Those 

 of llif firsl arc rounded : of the presenl one. compressed. The G. inlermedius 



