WEALDEN FORMATIONS. 23 



is but little trace of spinous process from the somewhat fractured summit of the 

 neural arch; this appears to be truncate in front, but has suffered some injury there, 

 permitting the fore part of the neural canal and the whole anterior articular ball to be 

 seeri in a direct vertical view (as in figs. 1 and 3, Tab. VI). The back part of the 

 neural arch appears to be deeply cleft through the backward production and divergence 

 of the posterior zygapophyses. 



In the collection of fossils of the late Mr. Saull, F.G.S., now in the Museum of the 

 Literary Institution, Aldersgate Street, London, there is a cervical vertebra of 

 Streptospondylus major, associated, as ia the Mantellian Collection, with vertebrae of 

 the Iguanodon and Cetiosaurus, all of which liave been washed out of the submarine 

 Wealden beds at the south side of the Isle of Wight, and thrown on shore near Culver 

 Cliffs and Brook Point. 



The lower half of the sides of the centrum of this vertebra of the Streptospondylus 

 are, like the preceding vertebra from Tilgate, concave and obliquely compressed, so as 

 to converge to the anterior part of the under surface (Tab. VI, fig. 2), which thus presents 

 a triangular form, with the apex forming the obtuse anterior ridge (/;), and the base 

 turned '.ackward and becoming somewdiat flattened. Each lateral concavity is bounded 

 above by a short but broad parapophysis (ib. p), developed from the anterior half of that 

 part of the centrum, and terminated by an oblong flattened surface for the articulation 

 of the head of the cervical rib ; which surface is about twice as long in the antero- 

 posterior as the vertical direction. Above this process the centrum is again concave, 

 but there is no pit or defined cavity behind its process. Tlie base of the neurapophysis 

 is anchylosed to nearly the wdiole antero-poslerior extent of the centrum, the course 

 of the original straight suture being, however, discernible. A diapophysis is developed 

 from the side of the base of the neurapophysis, affording a broader surface for the 

 tubercle of the cervical rib than does the parapophysis for the head. Above the 

 diapophysis the neurapophyses converge obliquely to the base of the spinous process. 

 Tlie line of the base of the spine inclines forward, and the thickness of the spine 

 diminishes in the same direction. The posterior zygapophyses in the cervical vertebra 

 from Culver Cliff", are similar in all respects to those in the Tilgate specimen, and 

 equally determine the fore and hind extremities of the vertebra. 



The difference in the height of the neural arch, and in the configuration of its 

 external surface, which both the cervical vertebree of the great Wealden Strepto- 

 spondijlus present, when compared with the dorsal vertebrae of the smaller species 

 from the older oolitic formations,* is very great ; and the more remarkable, as in the 

 existing Crocodiles the height of the neurapophyses is greater in the cervical than in the 

 dorsal region. Since, however, the diapophyses in the Crocodiles come off" from a higher 

 part of the neural arch in the dorsal than in the cervical vertebrae, the spine of the 

 great Wealden Slrepfospondj/Ius may possibly present modifications in the dorsal 



* atrepiosjwhdi/lus Gavieri, ' Ossenieiis Fossiles,' torn, cit., p. 308, pi. cc.\xxvi. 



