6 



this a deep linear foramen extends throughout the greater part of the length 

 of the centrum. If this vertebra possesses a diapophysis it is rudimental. 

 . The caudal vertebrae are amphiccelian, but not deeply so. They are 

 subquadrate in section and not so short as the corresponding ones of Hadro- 

 saurus. The most anterior one of the series has short robust diapophyses, 

 and is more concave anteriorly than posteriorly. The other caudals are 

 more equally bi-concave, but the cavity is very shallow on the most distal 

 of them. The centrum is also relatively more elongate and compressed 

 than those of the others. None of them display the lateral pneumatic 

 fossa which exists in the dorsals, and, where broken so as to permit a view 

 of the internal structure, the latter appears to consist of rather finely spongy 

 tissue. The chevron facets are not very well defined, and the neural 

 spines are of usual forms, and on the anterior two vertebrae, elongate. 



Several genera have been described which possess some of the features 

 presented by the one to which the present animal belongs. The following 

 are characterized by the presence of the lateral sinuses of the vertebral 

 centra: Megadactylus Hitch., Getiosaurus Owen., Omithapsis Seeley, 

 Botlirospondylus Ow., and Pneumatosteus Cope. The first of these may 

 be dismissed with the remark that its caudal vertebrae possess the sinuses 

 as well as the dorsals, which we have seen is not the case with the Colo- 

 rado animal. The centra of Cetiosaurus, according to Owen, and those of 

 Pneumatosteus do not exhibit the cavernous structure above described, 

 but are uniformly spongy interiorly. Ornithopsis, of Seeley, which Owen 

 refers to his subsequently described Botlirospondylus, possesses a cavernous 

 cellular internal structure, which I have not found in the reptile from 

 Canyon City, Colorado, but which occurs in another huge saurian discov- 

 ered by Prof. Lakes near Golden, Colorado, in the same stratigraphical 

 horizon. Another name (Chondrosteosaunos) has been introduced by 

 Prof. Owen, but he specifies no generic characters* nor points out how it 

 differs from Ornithopsis, which it resembles in its cellular structure. 



Prior to the reception of the present specimen, I was negotiating with 

 Prof. Arthur Lakes, of Golden, Colorado, for the acquisition of another 

 fossil skeleton of a gigantic saurian which he had discovered in that region. 

 This gentleman sent for my inspection two vertebral centra with other 

 fragments. Anticipating their purchase I made some remarks on their 

 characters before a meeting of the American Philosophical Society held on 

 July 20th of the present year. Before my arrangements with Prof. Lakes 

 were completed, the bones which he had found were purchased by Prof. 

 O. C. Marsh, of Yale College. The specimens in my possession were 

 thereupon sent to Prof. Marsh, and my proposed article withdrawn from 

 the hands of the printer. A short time previous to this, a portion of a 

 sacrum of a saurian found by Prof. Lakes had been noticed by Prof. Marsh 

 in the July number of the American Journal of Science and Arts, and he 

 had given names generic and specific to the animal to which it belongs. 

 That of the genus not being accompanied by any specific diagnosis nor 

 specific reference to its characters, has no claim to adoption according to 



