296 THE OSTEOLOGY OF THE REPTH^ES 



the neck. Lateral temporal openings small. Teeth with divided 

 roots in a single functional row. No teeth on premaxillae, the upper 

 jaws terminating in a distinct "rostral" bone. Vertebrae platy- 

 coelous, the first three or four cervicals coossiiied. Sacrum com- 

 posed of numerous vertebrae. lUum with long preacetabular and 

 postacetabular process. Ischium slender, curved, the postpubis 

 more or less vestigial. Carpus and tarsus reduced, but two carpaHa. 

 Astragalus firmly united with tibia, the calcaneum free; fifth toe 

 vestigial. 



Uppermost Cretaceous. Anchiceratops Brown, Brachyceratops Gil- 

 more, Ceratops Marsh, Chasmosaurus Lambe, Centrosaurus Lambe, 

 Diceratops Lull, Eoceratops Lambe, Leptoceratops Brown, Mono- 

 clonius Cope, Triceratops Marsh, Styracosaurus Lambe, Torosaurus 

 Marsh, Agathaumas Cope, Western North America. 



19. ORDER PTEROSAURIA 



Volant reptiles with highly ossified, pneumatic skeleton. Skull 

 elongated, more or less pointed, the external nares remote from the 

 tip. No parietal foramen. Orbits with sclerotic plates. Neck elon- 

 gate; eight or nine cervicals, ten or more dorsals, four to ten sacrals, 

 and about twelve to forty caudals; the presacrals procoelous, the 

 caudals amphicoelous. No supracoracoid foramen, clavicles, or in- 

 terclavicle. Sternum large, well ossified; parasternals present. Hu- 

 merus shorter than forearm, with large lateral process; carpus more 

 or less reduced; a pteroid bone articulating with carpus. First three 

 fingers small, with claws; fourth greatly elongated for support 

 of patagium; fifth digit absent. Prepubes articulating with pelvis. 

 Femora shorter than tibia; fibula reduced or absent; first tarsal row 

 more or less fused with tibia; feet long, pentadactylate, the fifth toe 

 more or less reduced. 



A. SUBORDER PTERODERMATA (RHAMPHORHYNCHOIDEA) 



Antorbital opening distinct. Jaws with teeth. Prevomers and 

 internal nares distinct. Orbits large. Free cervical ribs sometimes 

 present. Tail long, with a terminal dilatation. Metacarpals less 

 than half the length of the forearm, articulating with carpus. Fibula 

 present; lifth toe complete. 



