483 0. C. Marsh — Families of Sauropodous Dhwsauria. 



(2) Family Diplodocidce. External nares at apex of skull; 

 no depression for nasal gland ; two antorbital openings ; large 

 pituitary fossa; dentition weak, and in front of jaws only; 

 brain inclined backward; dentary bone narrow in front. 

 Scapula with shaft somewhat enlarged at summit. Ischia 

 with shaft expanded distally, directed downward and back- 

 ward, with sides meeting on median line. Sacrum hollow, 

 with three coossified vertebrae. Anterior caudal vertebra 

 proccelian, with sides deeply excavated, and cbevrons single ; 

 median caudals excavated below, with chevrons double, having 

 both anterior and posterior branches; distal caudals elongate, 

 with rodlike chevrons. 



Genera Diplodocus and Barosaurus. Jurassic, North 

 America. 



(3) Family Morosauridce. External nares anterior ; large 

 fossa for nasal gland ; small pituitary fossa ; dentary bone 

 massive in front ; teeth very large. Shaft of scapula expanded 

 at distal end ; coracoid suboval. Sacral vertebrae four in num- 

 ber, and nearly solid ; ischia slender, with twisted shaft directed 

 backward, and sides meeting on median line. Anterior caudals 

 solid ; chevrons single. 



Genera JMorosaumcs, Camarasaurus (?) (Amphiccelias). 

 Jurassic, North America and Europe. 



(4) Family Pleuroccdidw. Dentary bone constricted medi- 

 ally ; teeth w T ith crowns like those of Diplodocus. Cervical 

 vertebrae elongate, centra hollow, with large lateral openings; 

 sacral vertebrae solid, with lateral depressions in centra ; caudal 

 vertebrae solid ; anterior caudals with flat articular faces, and 

 transversely compressed neural spines ; median caudal vertebrae 

 with neural arches on front half of centra. Ischia with com- 

 pressed distal ends, and sides meeting on median line. 



Genera Pleuroccelus, Astrodon (?). Jurassic, North America 

 and Europe. Include the smallest known Sauropoda. 



(5) Family Cardiodontidce. Teeth of moderate size. Upper 

 end of scapula expanded ; humerus elongate ; fore limbs nearly 

 equaling hind limbs in length. Sacrum solid; ischia with 

 wide distal ends, and sides meeting on median line: Caudal 

 vertebrae biconcave; median caudals with double chevrons. 



Genera Cardiodon (Cetiosaurus), Bothriospondylus, Omi- 

 thopsis, and Pelorosaxirus. European, and probably all 

 Jurassic. 



(6) Family Titanosauridce. Fore limbs elongate ; coracoid 

 quadrilateral. Presacral vertebrae opisthoccelian ; first caudal 

 vertebrae biconvex ; remaining caudals proccelian ; chevrons 

 open above. 



Genera Titanosaurus and Argyrosaurus. Cretaceous (?), 

 India and Patagonia. 





