ON BRITISH FOSSIL. REPTILES. 91 



The two superior ridges, extending from the upper part of the anterior 

 and posterior oblique processes to the transverse process of the same side, 

 describe a regular concave curve. 



The vertical diameter of the fractured transverse process is 1 inch 3 lines, 

 its transverse diameter is 1 inch. 



The great development of the superior part of the neural arch, and the 

 strength and high relief of the buttress-like ridges supporting and strengthen- 

 ing the different processes, indicate that the spinous process was unusually- 

 large and massive. This process was not preserved in any of the vertebrae of 

 the Honfleur Streptospondylus described by Cuvier, nor, unfortunately, in 

 the present vertebra ; but its otherwise more perfect state adds another cha- 

 racter to those by which the vertebrae of the Streptospondylus deviate from 

 the Crocodilian type ; viz. a broad plate of bone extended transversely be- 

 tween the two posterior oblique processes, and increasing in breadth as it 

 ascends. The base from which the spinous process should rise, which is thus 

 bounded by the oblique and transverse pi'ocesses, extends beyond, and, as it 

 were, overhangs the whole body of the vertebra below ; and is hardly less re- 

 markable for the height to which it is canned above the body. 



Thus from the highest part of the posterior oblique process to the lower 

 margin of the corresponding articular surface of the vertebral centre mea- 

 sures 6 inches ; the length of the vertebral centrum being 3 inches 5 lines : 

 the contrary proportions prevail in the posterior dorsal and lumbar vertebrae 

 of the existing Crocodiles. The breadth of the neural arch, where the la- 

 teral buttresses terminate at the base of the transverse processes, is 6 inches. 



Streptospondylus major, nob. — The third British formation in which I have 

 determined the remains of the genus Streptospondylus is the Wealden ; the 

 specimens having been obtained from three localities, viz. Tilgate Forest in 

 Sussex, and Brook Point and Culver Cliff in the Isle of Wight. The speci- 

 mens differ in size from those already described, being larger than the Strep- 

 tospondylus Cuvieri from the oolite ; I strongly suspect that they indicate a 

 distinct species, but the means of comparison for the satisfactory establish- 

 ment of the distinctions are as yet wanting. M. H. von Meyer has added 

 nothing but the generic name to the observations of Cuvier, on which the 

 claims of the present extinct Crocodilian to generic distinction are founded : 

 these observations were taken from the dorsal vertebrae, atlas and axis, whilst 

 the most characteristic of the Wealden vertebrae appertain to the middle part 

 of the cervical region, from whence vertebrae of the reversed ball and socket 

 system have not been hitherto recognized. 



These vertebrae I apprehend to be those on which Dr. Mantell has founded 

 his description of the " Fourth system " from the Wealden. He says, " The 

 vertebrae of the fourth system (tig. 4) are very rare, only six or seven have 

 come under my observation. They are of the true Lacertian type, having the 

 articular facets of the body convex posteriorly and concave anteriorly, and 

 are loider than high, as in the Iguana and Monitors, and not in the reverse 

 proportions, as in the recent Crocodiles. In two large but mutilated cervi- 

 cals, the admeasurements are as follow : — 



Inch. 

 " Height of the concave extremity 85 



Width of the same 4^ 



« ' 



Length of the body 6 



■ It is not obvious whether the annular part be divided by suture or other- 

 wise ; the articular apophyses are horizontal and very strong ; the spinous 

 process is destroyed *." 



* MauteU's Geology of the South-east of England, 8vo, 1833, p. 300. 



