PKEPARATION AND RESEARCH IN AMERICAN MUSEUM 387 



1914 it was definitely adopted by Mook.^° At present Morosaurus is con- 

 sidered to be a synonym of Camarasaurus, Cope's term having priority 

 and therefore being valid. 



The basis for this conclusion is the following group of facts : both are 

 massive in proportions, though different in size; both the remains of 

 Camarasaurus herein described and those of the type specimens of Marsh's 

 various species of Morosaurus have .similar outlines to the bones of the 

 skull, so far as these are available for comparison ; the teeth are likewise 

 similar; the cervical vertebras, especially the axis, are practically identical 

 in form; the dorsal vertebrae have similar outlines and proportions and 

 are composed of essentially the same laminar elements and cavities ; they 

 have short spines, the division of the spines is similar, and the centra 

 exhibit the same kind of opisthocoelous articulations; the sacrum in each 

 possesses short spines of similar form and composition; also a tendency 

 toward retardation in the inclusion of the dorsosacral in the sacrum ; the 

 caudal vertebras have similar spines, similar centra, and similar slightly 

 retarded development of caudal ribs ; the scapula and coracoid are almost 

 identical in outline and arrangement of parts ; the ischia are slender, both 

 actually and in proportion to the other parts of the skeleton, having little 

 resemblance to other opisthocoelous ischia; the pubes are very angular in 

 outline and exhibit a similar form of twisting on the median borders ; the 

 limb-bone proportions are similar, so far as direct comparison is possible. 



The difference in size between the Camarasaurus remains now described 

 and those of the Marsh species is largely due to age distinctions. 



CHARACTERS OF THE GENUS AMPHICCELIAS 



Amphicoelias is more slender than Camarasaurus; its remains resemble 

 those of Diplodocus, but are somewhat larger than any known Diplodocus 

 and are somewhat more strongly constructed. 



The anterior dorsal vertebrae possess divided spines ; the spines of those 

 near the sacrum are single. The latter possess double pre- and post-spinal 

 laminae. The posterior dorsal centra are platycoelous to amphicoelous, 

 contrasting with the opisthocoelous centra of the posterior dorsal vertebrae 

 of Camarasaurus. The femur is long and slender. 



The following characters are inferred from material provisionally re- 

 ferred to the genus : scapula very large, resembling that of Diplodocus in 

 outline, but much more massive ; the angle between the longitudinal axis 

 and the axis connecting the anterior and posterior inferior processes is 

 oblique as in Diplodocus. The coracoid resembles that of Diplodocus in 



10 Charles C. Mook : Notes on Camarasaurus Cope. Ann. N. Y. Acad. Sci., vol, xxiv, 

 May 21, 1914. pp. 19-22, 1 fig. 



XXVII — Bull. Geol. Soc. Am., Vol. 30, 1918 



