228 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXXVI. 



After a comparison of Lj^dekker's figures of this specimen (see fig. 

 13) with the axis of Oamptosaunts, and noting the many similarities 

 in proportion and position of the processes, together with the presence 

 of an intercentrnm on both and the absence of a ventral keel on the 

 centrum of the British specimen, so plainl}^ shown on the axis of 



Fig. 13. — Left lateral, ventral, and anterior aspects of the axis of ax Orthopo- 

 Dus? dinosaur fro.m the Wealden of the Isle of Wight No. R. 141ii British 

 Museum. 1 nat. size, a, diapophyses : ft, parapopiiyses ; c, second intercentrum ; 

 (I, articulation fob odontoid process ; e, articulation for intercentrum of atlas. 

 After Lydekker. 



Ce7'atosaiirvs^ I am quite convinced that this axis pertains to one of 

 the orthopodous dinosaurs rather than to one of the carnivorous 

 forms. Tt might })ossibly be referred to Camptomurvs ? valdensis 

 Lvdekker, also from the Wealden of the Isle of AVight. 



MeuHnrcincnts of Specimen. Cat. \o. 5)73, U.S.N,M. 



mm. 



Greatest leufjtli of centrum of axis 55 



Greatest width anterior extremity 59 



Greatest width posterior extremity 45 



The third cervical. — The third cervical may be distinguished by its 

 plano-concave (platycoelian) centrum and by the fact that if the 

 planes of the articular surfaces were produced ventrally they would 

 intersect within a foot below the ventral surface of the centrum (see 

 Plate 12). In the succeeding cervicals just the opposite condition 

 is found, that is. the produced planes of their articular ends would 

 meet dorsally. In the articulated cervicals the u]iward curve of the 

 posterior cervicals changes with the third vertebra to a forward and 

 downward direction, thus giving the neck a graceful sigmoid curve 

 very bird-like in character. 



The lateral surface of the centrum is constricted transversely, but 

 flares out posteriorly. The centrum is more regularlv rounded, the 

 sides being convex vertically, and it lacks the decided ventral keel 

 found in the cervicals which follow. 



