Prof. 0. C. Marsh — Classification of Dinosaurs. 393 



biconcave. Pelvic bones coossified ; ilium expanded in front of 

 acetabulum ; pubes slender ; an interpubic bone ; iscbia slender, 

 witb distal ends coossified. Limb bones hollow ; manus with four 

 digits ; femur longer than tibia ; astragalus with ascending process ; 

 metatarsals coossified ; three digits only in pes. Osseous dermal 

 plates. (Figure 3.) 



Genus Ceralosaurus. Jurassic, North America. 



(9) Family Ornitlwmimidce. Pelvic bones coossified with each 

 other and with sacrum ; ilium expanded in front of acetabulum. 

 Limb bones very hollow ; fore limbs very small ; digits with very 

 long, pointed claws ; hind limbs of true avian type ; femur longer 

 than tibia ; feet digitigrade and unguiculate. 



Genus Omithomimus. Cretaceous, North America. 



Sub-order Hallopoda (Leaping foot). 



(10) Family Hallopidcc. Vertebrae and limb bones hollow ; 

 vertebrae biconcave ; two vertebras in sacrum ; acetabulum formed 

 by ilium, pubis, and ischium ; pubes rod-like, projecting downward, 

 but not coossified distally ; no postpubis ; iscbia with distal ends 

 expanded, meeting below on median line. Fore limbs very small, 

 with four digits in manus. Femur shorter than tibia; hind limbs 

 very long, with three digits only in pes, and metatarsals greatly 

 elongated ; astragalus without ascending process ; calcaneum much 

 produced backward ; feet digitigrade, unguiculate. 



Genus Hallopus. Jurassic, North America. 



Order Sauropoda (Lizard foot). Herbivorous. 



External naies at apex of skull ; premaxillary bones with teeth ; 

 teeth with rugose crowns more or less spoon-shaped ; large antorbital 

 openings ; no pineal foramen ; alisphenoid bones ; brain case ossified ; 

 no columellas ; postoccipital bones ; no predentary bone ; dentary 

 without coronoid process. Cervical ribs coossified with vertebras ; 

 anterior vertebras opisthoccelian, with neural spines bifid ; posterior 

 trunk vertebras united by diplosphenal articulation ; presacral verte- 

 bras hollow ; each sacral vertebra supports its own transverse process, 

 or sacral rib ; no diapophyses on sacral vertebras ; neural cavity much 

 expanded in sacrum ; first caudal vertebra procoslian. Sternal bones 

 parial ; sternal ribs ossified. Ilium expanded in front of acetabulum ; 

 pubes projecting in front, and united distally by cartilage ; no post- 

 pubis. Limb bones solid ; fore and hind limbs nearly equal ; 

 metacarpals longer than metatarsals; femur longer than tibia; 

 astragalus not fitted to end of tibia ; feet plantigrade, uugulate ; five 

 digits in manus and pes ; second row of carpal and tarsal bones 

 unossified ; locomotion quadrupedal. 



(1) Family Atlantosauridce. A pituitary canal ; large fossa for 

 nasal gland. Distal end of scapula not expanded. Sacrum hollow ; 

 iscbia directed downward, with expanded extremities meeting on 

 median line. Anterior caudal vertebras with lateral cavities ; 

 remaining; caudals solid. 



