marsh.] SAUROPODA. 241 



mauus; femur shorter than tibia; hind limbs very long, with three 

 functional digits in pes, aud metatarsals greatly elongated; astragalus 

 without ascending process ; calcaneum much produced backward ; feet 

 digitigrade, nnguiculate. (PI. VI.) 

 Genus Hallopus. Jurassic, North America. 



Order Satjropoda (Lizard foot). ' Herbivorous. 



External nares at apes of skull; premaxillary bones with teeth; 

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

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

 columella?; postoccipital bones; no predentary bone; dentary Avithout 

 coronoid process. Cervical ribs coossified with vertebrae; anterior ver- 

 tebrae opisthoccelian, with neural spines bifid; posterior trunk vertebra? 

 united by diplospheual articulation; presacral vertebra? hollow; each 

 sacral vertebra supports it own transverse process, or sacral rib; no 

 diapophyses on sacral vertebra? ; neural canal much expanded in 

 sacrum; first caudal vertebra? proccelian. Sternal bones parial; ster- 

 nal ribs ossified. Ilium expanded in front of acetabulum; pubes pro- 

 jecting in front, and united distally by cartilage; no postpubis. 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, ungulate ; five digits in manus aud pes; second 

 row of carpal and tarsal bones unossified; locomotion quadrupedal. 



(1) Family Atlantosaurida?. A pituitary canal; large fossa for nasal 

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

 directed downward, with expanded extremities meeting on median 

 line. Anterior caudal vertebra? with lateral cavities; remaining cau- 

 dals solid. (Pis. XY-XXIY, and XLII.) 



Genera Atlantosaurus, Apatosaurus, Barosaurus, Brontosaurus. 

 Include the largest known land animals. Jurassic, Xorth America. 



(2) Family Diplodocida?. External nares superior; no depression 

 for nasal gland: two antorbital openings; large pituitary fossa; denti- 

 tion weak, and in front of jaws only; brain inclined backward; dentary 

 bone narrow in front. Ischia with shaft not expanded distally, directed 

 downward and backward, with sides meeting on median lines. Sacrum 

 hollow, with three vertebra?. Caudal vertebra? deeply excavated below ; 

 chevrons with both auterior and posterior branches. (Pis. XXV- 

 XXIX.) 



Genus Diplodocus. Jurassic, Xorth America. 



(3) Family Morosaurida?. External nares lateral; large fossa for 

 nasal gland; small pituitary fossa; dentary bone massive in front; 

 teeth very large. Shaft of scapula expanded at distal end. Sacral ver- 

 tebra? four in number, and nearly solid; ischia slender, with twisted 

 shaft directed backward, and sides meeting on median line. Anterior 

 caudals solid. (Pis. XXIX-XXXVIII.) 



Genera Morosanrus, Camarasaurus (?) (Amphiccelias). Jurassic, 

 Xorth America. 



16 GEOL, pt 1 16 



