4 FOSSIL REPTILTA OF THE 



and of the third cervical vertebra ( a , 3) with parts of the pleurapophyses of the 

 atlas (pi. a) and axis (pi. x) ; it includes, also, large, massive dermal bones external 

 and superior to the vertebral elements. The centrum of the axis is 1 inch 3 lines 

 in length, from the line of adhesion of that of the atlas, part of which remains 

 connected, as the " odontoid process ;'' the proper body of the axis is subcarinate 

 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 (pl'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 (3) 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 are worked out more completely 

 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, 6) which is pre- 

 served, 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 (pi) articulates by a bifurcate 

 end with both par- and di- apophyses : the upper transverse process (fig. 4, d) 

 extends nearly 1^ inch from the neural arch ; the neural canal ( n ) 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 portion of the 

 articular surface which is preserved (z») of the centrum of the seventh vertebra 

 indicates the same feeble concavity as in the preceding cervical vertebra (fig. 3). 



Supposing the vertebra (Tab. 1, 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 vertebrae, assuming in them a hatchet-like 

 shape, with an overlapping arrangement; the posterior production of the " blade " 



