cope.] ADO: [Dec. 21, 



terior limbs. The scapula is enormous as compared with the pelvic bones I 

 The sacrum is also small and short, showing that the weight was not borne 

 on the hinder limbs. The great length of the humerus in the probably 

 allied genus Dystrophins, from the Trias of Utah, adds to the probability 

 that the same bones were large in Gamarasaurus. This character, taken 

 in connection with the remarkably long neck possessed by that genus, 

 suggests a resemblance in form and habits between those huge reptiles and 

 the giraffe. While some of the later Dinosauria elevated themselves on 

 their hind limbs to reach the tree-tops on which they fed, the general form 

 of the body in some of these earlier types enabled them to reach their food 

 without the anterior limbs leaving the earth. 



Another remarkable peculiarity which these genera share with Dystro- 

 phins and Cetiosaurus is the irregular and pitted character of the articular 

 extremities of some of the bones. This indicates a cartilaginous covering, 

 and probably in some instances an osseous cap or epiplysis. 



Dr. Hayclen visited the locality of Mr. Lucas' excavations, and informs 

 me that the formation from which the Gamarasaums was obtained, is the 

 Dakota. Prof. Marsh has attempted to identify what is, according to Prof. 

 Mudge, the same horizon, one hundred miles north of Canyon City, with 

 the Wealden of England. Specimens from the northern locality which I 

 have examined render it certain that the horizon is that of Mr. Lucas' ex- 

 cavations. Of this I may say that there is no paleontological evidence of 

 its identity with the Wealden . The resemblance of the vertebrate fossils 

 to those of the English Oolite is much greater, but not sufficient as yet for 

 identification. 



The discovery of Vertebrata in the strata of the Dakota epoch is an im- 

 portant addition to the geology and paleontology of North America. The 

 numerous geologists who have explored its outcrops have failed hitherto 

 to observe remains of this class of animals. Credit is due to Superintendent 

 O. W. Lucas for this discovery, and also in an especial manner for the 

 skill and care he has exercised in taking out and shipping the ponderous 

 specimens. 



CAMARASAURUS Cope. 



Palseontological Bulletin No. 25, p. 5 ; (published August 23, 1877). 



The characters of this genus are derived from nearly all portions of the 

 skeleton excepting the skull and ungues. The bones are generally in good 

 preservation. 



The vertebrae of the cervical, dorsal and lumbar region are all opistho- 

 coelous or reversed ball and socket. The centra of the cervicals are very 

 elongate, but those which follow them diminish rapidly in* length, until in 

 the lumbar region they have but a small anteroposterior diameter. The 

 anterior caudal vertebra? are also very short and wide ; but the length of 

 the centra gradually increases, so that the distal ones are quite elongate. 

 The caudal centra are all moderately amphicoelous. 



The centra of the cervicals and dorsals are hollow, and the interior 



