102 BRITISH FOSSIL REPTILES. 



below ; gently concave lengthwise at the sides ; compressed in the same degree at 

 the middle, and slightly expanded at the extremities. The rib which it sup- 

 ported {pV x) is shorter than that of the atlas, but, like it, is slender and straight ; 

 about 3 inches of the atlantal rib is preserved, and about 2 inches of that of 

 the axis. 



The body of the third vertebra presents a general increase of size ; it is 1 inch 

 8 lines in length, 2 inches 3 lines across the parapophyses at the fore part of the 

 vertebra, 1 inch 6 lines across the posterior articular surface, and 1 inch 2 lines 

 in depth. It is subcompressed at the sides, and more obtusely ridged below than 

 the axis. The fore part of the body is articulated by an almost flattened surface 

 with that at the back of the axis. 



The characters of the terminal articular surfaces were worked out more com- 

 pletely in a consecutive cervical vertebra detached from the third block, and which, 

 from its size, is probably the sixth. The part of the front surface (fig. 4, e) which 

 is preserved is flat with a convex periphery ; the hind surface (fig. 3, c) is slightly 

 concave, with a narrower and better defined circumference. The body of this 

 vertebra is 1 inch 10 lines in length, 2 inches 3 lines across the parapophyses (p) ; 

 1 inch 8 lines across the hinder articular end (c). The under part of the centrum 

 presents near its fore end a hypapophysial tuberosity ; it is constricted at the 

 middle, and a small venous canal opens into that concavity on either side. The rib 

 articulates by a bifurcate end with both par- and diapophyses ; the upper trans- 

 verse process (fig. 4, rf) extends nearly 1^ inch from the neural arch; the neural 

 canal («) is of a full oval form, with the small end downwards ; it is 9 inches in 

 its longest diameter. The breadth of the neural arch, below the diapophyses, is 

 1 inch 7 lines. 



In the portion of the succeeding cervical vertebra, from the same block, the 

 rib is directed more outwardly than in the antecedent one. The length of the 

 neck of the rib is 1 inch 2 lines ; its thickness 6 lines, which increases after the 

 development of the tubercle, where the fracture shows a subtriedral section. The 

 poi'tion of the articular surface which is preserved of the centrum of the second 

 vertebra indicates the same feeble concavity as in the preceding cervical vertebra 



(fig. 3). 



Supposing the vertebra (PI. 48. figs. 3 and 4) to be the sixth of the cervical 

 series, it shows that the rib has more speedily resumed its normal character than 

 in the Crocodilia. In these large existing Saurians the pleurapophysis, slender, 

 straight and rather long, in the atlas and axis, becomes shortened and expanded 

 in the third, fourth, fifth, and sixth cervical vertebrse, assuming in them a hatchet- 

 like shape, with an overlapping arrangement; the posterior production of the 

 "blade" lengthens in the seventh cervical; but the ordinary rib-shape is only 

 resumed in the eighth vertebra, regarded as the first dorsal by Cuvier. 



