J. W. HULKE ON THE VERTEBE^ OF 0ENITH0PSI3. 31 



4. SirppLEM:ENTAET ISToTE Oil the YERTEBEyE o/ Oenithopsis, Seeley,=s 

 Efcamergtus, EuRe. By J. ^Y. Hulke, Esq., F.R.S., P.G.S. 

 (Eead November 19, 1879.) 



[Plates III. & IV.] 



At the close of last session I brought before the Society some ad- 

 ditional evidence of the existence in our Wealden times of a huge 

 Dinosaur Trhose vertebrae were characterized by marvellous light- 

 ness ; and I endeavoured to show, by an examination of all the 

 material at that time available for comparison, that although the 

 vertebrae of this Saiiimji (OrnitJioj)sis, Seeley, Bucamerotus, Hulke ; 

 Botliriospondylus, in part, CJiondrosteosaurits, Owen) exhibited 

 correspondences with those of certain newly discovered American 

 forms (some of which had been recently noticed by Prof. Owen) 

 which indicated affinity with these, yet there coexisted such differ- 

 ences as seemed to me to disprove their generic identity. 



The liberality of the Eev. W. Fox now enables me to place before 

 you photographs and drawings which, for the first time, afford com- 

 plete information respecting the structure of the vertebral column in 

 the neck aud trunk of this remarkable animal. 



Necl\ — Three cervical vertebras in Mr. Fox's possession show the 

 centrum in this region to be strongly opisthocoelous. The articular 

 ball in this region is a larger portion of a sphere than in the trunk, 

 and the cup is correspondingly deeper. The under surface of the 

 centrum is singularly flat, a character which disappears in passing 

 backwards and is little apparent in the trunk. The neural canal is 

 very capacious. The prsezygapophyses project considerably for- 

 ward beyond the front of the neural arch, overhanging here the 

 ball. Their articulating surface is large, of a roughly oblong form, 

 and directed upwards and inwards. It is a single surface for each 

 prsezygapophysis ; and the notch between the preezygapophyses is 

 non- articular. The additional articular surface forming the zygan- 

 tral arrangement present in dorsal centra is here absent ; and the 

 associated zygosphenal bolt dependent from the confluent inner ends 

 of the postzygapophyses is necessarily also wanting in the neck. 

 The neural arch in all Mr. Fox's specimens referable to the neck is 

 devoid of spinous process. From the root of each prsezygapophysis 

 a lofty crest curves upwards, backwards, and inwards, and then 

 diverges and declines posteriorly, where it ends in a stout postzyga- 

 pophysial process bearing on its under and outer surface the articular 

 facet. The crests of opposite sides are separated by a mesial groove 

 very deep in front. There are two transverse processes, a lower on 

 the body and an upper on the arch. The lower transverse process 

 (parapophysis) springs from the side of the centrum towards the 

 front, a constriction separating it from the articular ball. From tho 

 parapophysis a projecting ledge-like plate passes backwards along 

 the centrum to its posterior border. The upper transverse process 



