AND PELVIC BONES OF PLIOSAURUS EVANSI. 719 



pedicles of the neurapophyses strong and ovate in section and mode- 

 rately compressed from side to side, and thns far different from the 

 typical nenral arch in Kimmeridge-clay species of Pliosaurus. The 

 neural spine is not preserved. The rib has a divided articular head, 

 the two parts being separated by a transverse groove. 



The rib is 1-J inch long, is compressed from above downward, 

 more and more so to its extremity ; and it is compressed from side to 

 side, but at its free end expands from behind forward. The proximal 

 end is lg inch deep ; the distal end is 1| inch wide. 



The eleventh cervical has the centrum If inch long, 2J- inches 

 deep, and 3g inches wide transversely on the posterior face. The 

 articular surfaces for the neural arch are more horizontal, somewhat 

 narrower ; and each is distinctly four-sided. There is a large oval 

 vascular impression adjoining the middle of the neurapophysial facet 

 on each side. 



The pedicles for the ribs are more elevated, though still less than 

 half an inch high ; they are nearer to the posterior margin of the 

 vertebra. The base of the centrum is already becoming more rounded 

 from side to side. 



The seventeenth vertebra has the articular face of the centrum 

 3| inches broad and nearly 3 inches deep. It is of more elliptical 

 outline than the preceding vertebrae, and has the articular face 

 flatter, but preserves the central depression. The antero-posterior 

 measurement at the base is 1\^ inch. The base has become more 

 convex from side to side, and measures transversely, between the 

 bases of the pedicles for the ribs, 2-| inches. The articular faces of 

 these pedicles are vertically ovate, If inch deep, l T ?g- inch wide, 

 concave, and without any trace of division ; so that the head of the 

 rib may now be presumed to have become single. The articular 

 areas for the neural arch are relatively narrower, and the width of 

 the flat surface of the neural canal is greater, than in the preceding 

 vertebras. 



The 19th vertebra has the rib preserved in contact with the centrum; 

 its articular end has an elevated tubercle such as would fit into the 

 depression on the corresponding pedicle on the side of the centrum. 

 This is about the last true cervical vertebra ; for in the 20th the 

 articulation for the rib has risen so high as to be partly supported 

 on the neural arch. The base of the centrum has necessarily become 

 much more convex from side to side. The face of the centrum is 

 3 inches deep. The 21st vertebra also has the rib partly on the 

 centrum and partly on the neural arch ; and therefore these two 

 vertebras between the neck and the back form the region named 

 pectoral. 



Dorsal Vertebrae (figs. 5, 6). 



The 22nd centrum may be regarded as the first dorsal. The 

 intervertebral articular face has become much more nearly circular, 

 being 3-J- inches deep, and 3-| inches wide. The articular faces are 

 slightly concave, with a large ill-defined eminence below the middle — 

 a character also seen in subsequent vertebras. The centrum is com- 



