70 REPORT — 1839. 



sions are elliptical, narrower than in the PL macrocephalusy but 

 broader than in the PL Hawkinsii. In the 20th cervical ver- 

 tebra the costal is situated immediately below the neurapo- 

 physial pit ; but in the vertebrae anterior to this, they are sepa- 

 rated from the neurapophysial pits by a space equal to their own 

 breadth. This is a character which distinguishes the present 

 species very satisfactorily from the PL macrocejjhalus. From 

 the PL Haivkivisii it differs in the greater relative size of 

 the cervical vertebrae ; and especially in the superior height of 

 the neurapophyses, which fully equals the vertical diameter of 

 the vertebral body. 



The anterior and posterior margins of the sides of the verte- 

 bral body are impressed with fine irregular longitudinal ridges, 

 but the midspace between the costal and neurapophysial de- 

 pressions is quite smooth. The spines of the anterior cervical 

 vertebrae are obliquely truncate at the anterior margin, and are 

 less square-shaped and less strong than in the PL macrocepha- 

 his. The characteristic vascular foramina on the inferior sur- 

 face of the centrum lie in deep concavities, and are separated 

 by a longitudinal ridge. This ridge gradually disappears in the 

 dorsal vertebrae, and the vascular foramina become more widely 

 separated and approach the lateral aspects of the centrum. The 

 length of the 15th cervical vertebra is 1 in, 8 lines, its ver- 

 tical diameter 2 in. 2 lines. 



From the position in which the vertebrae lie in their lias ma- 

 trix, it wovild seem that an elastic intervertebral cushion of from 

 two to three lines thick had been interposed between their bo- 

 dies. The cervical ribs have their expanded or hatchet-shaped 

 extremities supported on longer pedicles than in the PL doli- 

 chodeirus or Hawkinsii. and in this respect they resemble 

 those of the PL macrocejjhalus. The spinous processes of 

 the dorsal region are stout and broad, quadrilateral, truncate 

 above, and with the angles very slightly rounded off ; they are 

 somewhat longer than those of the cervical vertebrae. The cau- 

 dal vertebrae appear to be less numerous than in the PL doli- 

 chodeirus or PL Hawkinsii. 



The caudal ribs appear to be expanded at their extremities, 

 somewhat analogously to the cervical ribs ; the depressions on 

 the sides of the vertebrae to which they are articulated are round, 

 and have their margins raised ; they are situated immediately 

 beneath the neurapophysial pits in the posterior caudal vertebrae. 

 The under part of the caudal vertebrae is concave, and presents 

 two vascular foramina on each side, separated by wide inter- 

 spaces. 



