153 



Width of tho preinaxillary at the second tooth 0. 041 



Leugth of the dentary 0. 245 



Length of a maxillary tooth 0.030 



Length of the maxillary tooth, crown only 0. 023 



Length of the os quadratum 0. 07? 



"Width of tho os quadratum distally 0. 045 



Length of the parietal 0. 085 



Length of the frontal to the Dares (median) .' 0. 110 



Width of the frontal between the orbits 0. 077 



Total length of the cranium (18.75 inches) 0. 473 



Platecarpus crassaetus. Cope. 



This saurian, which is of larger size than the last, is represented by a 

 series of dorsal, lumbar, and caudal vertebrae, with some bones of the limbs. 



The vertebrae are as much distinguished for their shortness as those 

 of P. latispinis are for their elongation. The articular faces are but little 

 broader than deep, and their planes are slightly oblique. They are very slightly 

 truncate above by the neural canal. The inferior face is somewhat concave 

 in the longitudinal direction. The zygapophyses are stout, and there are no 

 distinct rudiments of zygosphen. 



The dorsal vertebrae best preserved are those in which the diapophyses 

 reach the middle of the sides of the centra, and have no horizontal limb. 

 The latter are narrow, and have not extensive articular extremital surfaces. 



The lumbars and anterior caudals have round articular surfaces. One 

 of the latter, with strong diapophyses, but posterior, is subpentagona.l in 

 outline of cup. 



This species furnished the materials for the first description of the 

 posterior extremities in this order of reptiles. The humerus is a remarkable 

 bone, having the outline of that of Clidastes propython, Cope, but is very 

 much stouter, the antero-posterior dimensions of the proximal extremity 

 being greatly enlarged. The long diameters of the two extremities are, in 

 fact, nearly at right angles, instead of in the same plane; and the outline 

 of the proximal is subtriangular, one of the angles being prolonged into a 

 strong deltoid crest on the outer face of the bone, which extends half its 

 length. The inner or posterior distal angle is much produced ; while the 

 distal extremity is a flat, slightly-curved, diamond-shaped surface. The fibula 

 is as broad as long and three-quarters of a disk. The phalanges are stout, 

 thick, and depressed, thus differing much from those of Platecarpus ictericus, 

 A bone which I cannot assign to any other position than that of femur has 

 20 c 



