ON BRITISH FOSSIL REPTILES. 93 



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

 than in the dorsal region : as, however, the transverse processes in the Cro- 

 codiles come off from a higher part of the neural arch in the dorsal than in 

 the cervical vertebrae, the spine of the great Wealden Streptospondylus may 

 possibly present modifications in the dorsal region corresponding with those 

 remarkable ones which have been already described in the Whitby vertebra. 

 The posterior articular processes in the cervical vertebra from Culver Point, 

 are similar in all respects to those in the Tilgate specimen, and equally de- 

 termine the fore and hind extremities of the vertebra. 



The following are admeasurements of the bodies of the two vertebrae of 

 the Wealden Streptospondyhcs : — Tilgate. Culver Cliff. 



Inch. Lines. Inch. Lines. 



Transverse diameter of posterior concave 



articular surface 5 6 



Vertical diameter of posterior concave ar- 

 ticular surface 3 6 4 6 



Antero-posterior diameter 6 5* 



Transverse diameter of the body across 



the inferior transverse processes ... 6 66 



Height from lower surface of centrum 



to the hind part of base of spine . . 7 9 

 Antero-posterior extent of lower trans- 

 verse process 2 2 2 4< 



Interspace between upper and lower trans- 

 verse processes 2 



In the museum of the Geological Society of London there is a collection 

 of rolled vertebra? from the coast at Brook Point, Isle of Wight, whicli, among 

 the bones of Iguanodon and other gigantic Wealden genera, contains the 

 centrum or body of a dorsal vertebra of the great Streptospondylus. This 

 specimen, though much rolled and worn, is interesting, inasmuch as it ex- 

 hibits the characteristic contraction of the middle and expansion of the ends 

 of the centrum, together with unequivocal evidences of the marked depres- 

 sion on each side, near the upper part of the anterior or convex end of the 

 centrum. What remains of the depression is about the size of the end of a 

 man's thumb. The convexity of the anterior extremity resembles in degree, 

 and likewise in irregularity, that in the fractured vertebra of the Streptospon- 

 dylus from the oolite, in Mr. Kingdon's collection. 



The present centrum is less depressed than those of the cervical region, 

 but agrees with them in length, as the following dimensions show : — ■ 



Inches. Lines. 



Antero-posterior diameter 5\ 



Vertical diameter of concave end .... 5 6 



Transverse diameter of concave end ... 5 3 



Transverse diameter of middle of centrum . 3 



The vertebra from the forest marble alluded to in the note at p. 297 of 



Dr. Mantell's ' Geology of the South-east of England,' is a centrum from the 



posterior part of the dorsal region of the Streptospondylus major. 



The determination of the true nature of the convexo-concave vertebrae of 

 the Wealden, and of the affinities of the reptile to which tliey belonged, be- 

 sides extending our knowledge of the gigantic oviparous animals of that 



* It is evident that an inch at least, perhaps more, has been chiseled away from the ball 

 wliich terminated the anterior end of the body of the specimen in Mr. SauU's collection. 



t The margins of the extremities being worn and rounded prevent the actual length being 

 given. 



