ORDER DINOSAURIA. 



II/3 



Family Atlantosaurid^. — This name may be provisionally 

 adopted for a family which is represented by the genera Atlanto- 

 saurus, Apatosaurus, and Brontosaurus, of the Upper Jurassic of 

 North America, as well as by allied European types. In these huge 

 forms the ischium (fig. 1073) is directed downwards, and its shaft is 

 thick and not bent upon itself; while the humerus is comparatively 

 slender ; and the chevrons of the caudal vertebrae have their superior 

 extremities united. The teeth have the summit of the crown not 



Fig. 1074. — Posterior view of an anterior dorsal vertebra 0iCa7nara.sa.urus suftremus', from 

 the Upper Jurassic of North America. Reduced. (After Cope.) • 



much incurved. Apparently closely allied to, if not identical with, 

 some of the above-mentioned genera are Amphicoelias and Camara- 

 saurus of the same formations. An anterior dorsal vertebra of 

 the latter genus is represented in the accompanying woodcut ; this 

 vertebra is transitional between the cervicals and later dorsals, the 

 neural spine of the latter being absent. 



Professor Marsh estimates the total length of Broiitosaurus at upwards 

 of fifty feet, and its weight at more than twenty tons ; and Pelorosaurus, 

 of the English Wealden, must have been fully equal to these dimensions. 

 In respect of the former, the learned American palaeontologist observes, 

 " that the animal at times assumed a more erect position than is repre- 

 sented in the restoration is probable, but locomotion on the posterior 



