the rules of nomenclature, nor can the genus be distinguished from some 

 of those above enumerated from the few characters of mixed significance 

 which are mentioned. Especially is there nothing to indicate that it 

 differs from Omithopsis or Botlirospondylus. 



The opportunity of studying the dorsal and caudal vertebrae of the sau- 

 rian discovered by Professor Lakes, enables me to point out the characters 

 in which the animal from Canyon City differs from it. The centrum of 

 the dorsal vertebra from near Golden is concave posteriorly and plane an- 

 teriorly, instead of being convex anteriorly. The supposed caudal is 

 larger than the dorsal vertebra, while that of my specimen is smaller 

 than that of the dorsal centra. The articular faces are nearly plane, not 

 bi-concave, and the antero- posterior diameter of the centrum is dispro- 

 portionately small, as in Hadrosaurus. It has a lateral fossa, and its in- 

 terior is cavernous. A detached neural spine of this saurian has a form not 

 widely different from what is usual in these reptiles, and totally unlike the 

 extraordinary shape of the present genus. 



On such grounds I regard the present species as representing a genus 

 hitherto unknown, which may be called Camarasaurus and the species : 



Camarasaurus supremus. 



Many peculiarities are exhibited by the vertebrae of this species, which 

 are not described in saurians known up to the present time. Many of these 

 would have been lost in less careful hands .than those of Mr. Lucas, and 

 science is much indebted to him for the preservation of many thin os- 

 seous walls and buttresses. In general, the external walls of the cen- 

 tra are thin, and the processes are composed of laminae, united by narrow 

 margins. The vertebrae are lighter in proportion to their bulk than in any 

 air-breathing vertebrate. 



The anterior extremity of the centrum of the cervical vertebra is promi- 

 nently convex, and much depressed. The posterior and concave extremity 

 is wider, and of rather greater vertical diameter. The base of the neural 

 arch only occupies half of the length of the centrum, an equal extent of 

 the superior surface extending freely beyond it at its anterior and posterior 

 extremities, 



The linear lateral foramen commences a little behind the anterior base of 

 the neural arch, and descending somewhat in its direction, terminates be- 

 neath the posterior extremity of the base of the neural arch. The base of 

 the latter overhangs the foramen and the base of the transverse process. 

 The inferior surface of the centrum is concave, the concavity being 

 bounded in front by the inferior convex thickening of the extremity. Be- 

 hind the middle the surface becomes plane, and is, near the posterior ex- 

 tremity, bounded on each side by a short, angular ridge. 



Measurements. M. 

 Length of centrum between anterior convexity and pos- 

 terior lip 565 



Depth of posterior cup .090 



