242 DINOSAURS OF NORTH AMERICA. 



(4) Family Pleuroccelidae. Dentition weak; teeth resembling those 

 of Diplodocns. Cervical vertebra? elongated; centrum hollow, with 

 large lateral openings; sacral vertebra? solid, with lateral depressions 

 in centra; caudal vertebrae solid; anterior caudals with flat articular 

 faces and transversely compressed neural spines; middle caudal verte- 

 bra? with neural arch on front half of centrum. Ischia with compressed 

 distal ends, meeting on median line. (Pis. XL and XLI.) 



Genera Pleuroccelus, Astrodon ( !). Potomac, North America. 



(5) Family Titanosaurida?. Fore limbs elongate; coracoid quadri- 

 lateral. Presacral vertebra? opisthocoelian ; first caudal vertebra bicon- 

 vex; remaining caudals procoelian; chevrons open above- 

 Genera Titanosaurus and Argyrosaurus. Cretaceous ( ?), India and 



Patagonia. 



(6) Family Cardiodontida?. Teeth of moderate size. Upper end of 

 scapula expanded; humerus elongate; fore limbs near equaling hind 

 limbs in length. Sacrum solid ; ischia with wide distal ends meeting 

 on median line. Caudal vertebrae biconcave. 



Genera Cardiodon (Cetiosaurus), Bothriospondylus, Ornithopsis, and 

 Pelorosaurus. European, and probably all Jurassic. ' 



Order Predentata. Herbivorous. 



Narial opening lateral; no antorbital foramen; brain case ossified; 

 supraorbital bones; teeth with sculptured crowns; maxillary teeth with 

 crownsgrooved on outside; lower teeth with grooves on inside of crown ; 

 apredentary bone; dentary with coronoid process. Cervical ribs articu- 

 latingwith vertebra?; each sacral rib supported by two vertebra?. Ilium 

 elongated in front of acetabulum; prepubic bones free in front; post- 

 pubic bones present; ischia slender, directed backward, with distal 

 ends meeting side to side. Astragalus without ascending process. 



Suborder Stegosauria (Plated lizard). 



Skull without horns; no teeth in premaxillaries; teeth with distinct 

 compressed crowns and serrated edges. Vertebra? and limb bones 

 solid. Pubes projecting free in front; postpubis present. Fore limbs 

 small; femur longer than tibia; feet plantigrade, ungulate; five 

 digits in manus and four in pes; second row of carpals and tarsals 

 unossified ; locomotion mainly quadrupedal. Osseous dermal armor. 



(1) Family Stegosaurkke. Vertebra? biconcave. Neural canal in 

 sacrum expanded into large chamber; ischia directed backward, with 

 sides meeting on median line. Dorsal ribs T-shaped in cross section. 

 Astragalus coossified with tibia ; metapodials very short. Back sur- 

 mounted by a crest of vertical plates; tail armed with large spines. 

 (Pis. XLIII-LII.) 



Genera Stegosaurus (Hypsivhophus), Diracodon, Pala?osciucus, Pri- 

 conodon, all from North America; and in Europe, Omosaurus, Owen. 

 Jurassic and Cretaceous. 



1 The Wealden is here regarded as upper Jurassic, and not Cretaceous. See American Journal of 

 Science, Vol. L, p. 412, November, 1895. 



