WILLISTON: RANGE AND DISTRIBUTION OF THE MOSASAURS. 181 
PLATECARPINA. 
Hind feet functionally pentadactylate. Trunk short, the tail 
proportionally long, not dilated distally. Carpus and tarsus im- 
perfectly ossified. Vertebra. with rudimentary or functional zygos- 
phene. Premaxillary not projecting beyond the teeth, very obtuse. 
Quadrate large, with long suprastapedial process. 
Platecarpus Cope. 
Upper Turonian of Kansas and Colorado (Niobrara). 
? Senonian of Mississippi. 
Plioplatecarpus Dollo 
Lower Mestrichtian of Belgium (Danian). 
Prognathosaurus Dollo. 
Upper Senonian of Belgium (Brown Phosphate of Cipley). 
? Brachysaurus Williston 
Senonian of Dakota (Ft. Pierre). 
Sironectes Cope and Holosaurus Marsh 
Upper Turonian of Kansas (Niobrara). 
Taniwhasaurus Hector 
Upper Cenomanian of New Zealand. 
MOSASAURINZ. 
Hind feet tetradactylate. Carpus and tarsus fully ossified, and 
with not more than six phalanges in any digit. Trunk relatively 
long, the thorax short, the tail much compressed distally, the 
chevrons co-ossified with the centra. Zygosphenes rudimentary or 
functional. Humerus with a strong radial process at distal end. 
Prefrontal more or less dilated into a horizontal plate posteriorly. , 
Coronoid large. Rostrum short, obtusely conical. Quadrate small, 
with a suprastapedial process of moderate length. 
Moegasaurus Conybeare 
Lower Danian of Belgiuni and England (Upper and Lower 
Meestrichtian and Upper Chalk). 
Upper Senonian of Belgium (Brown Phosphate of Cipley). 
Senonian of New Jersey and Dakota (Greensand and 1 
ot, 
Pierre). 
? Senonian of Alabama and North Carolina. 
OClidastes Cope. 
Uppermost Turonian or Lowermost Senonian of Kansas and 
Colorado (Niobrara and Ft. Pierre). 
Senonian of New Jersey, Alabama and Mississippi. 
