THECOSPONDYLFS DAVIESI. 83 



has become narrowed to about one half of the anterior width. A 

 long foramen runs in the anterior part of the left lateral angle of 

 the base. 



The posterior vertical fracture of the specimen has been polished 

 (fig. 4) ; it shows the vertical height of the vertebra to be 4 centim. 

 The transverse width of the neural arch at its superior expansion 

 was 2-3 centim. ; the transverse width at the neuro-central suture is 

 1*7 centim., and at the base 1 centim. The height of the centrum 

 to the neural canal is 13 millim. : so its form is vertically oblong in 

 section, concave above and at the sides, and margined all round by a 

 thin wall of dense bony tissue, forming a perfect box, as in the ver- 

 tebra of an Ornithosaur. The neural canal is slightly higher than 

 wide, and measures 1 centim. transversely. The lateral walls of the 

 neural canal are thick, 3 millim. on the left side, and 4 millim. on 

 the right side, which includes two small foramina. The section of 

 the neural arch is subpentagonal. It is divided into four chambers. 

 Pirst, a vertically oblong cavity with the angles rounded (n) is placed 

 above the neural canal ; secondly, a small and narrow isosceles tri- 

 angle extends from above that cavity to the neural ridge (sn). Exter- 

 nally on each side are the large lateral subtriangular chambers (ln). 

 These cavities are defined by the thinnest films of bone (fig. 4). 



From this fragment it is only possible to attempt a restoration of 

 the vertebra on the basis of general principles and the structure of 

 allied animals ; and such an outline, of the natural size, is here 

 given (fig. 5). 



Fig. 5. — Outline of the Vertebra of Thecospondylus Daviesi, restored. 



IS at. size. 



The restoration, no less than the specimen described, indicates a 

 close resemblance and affinity with the cervical vertebra of Coelurus 

 fragiJis, Marsh*, which I suppose to indicate an animal not more 

 than two thirds as large as this, or smaller. Both have a similar 

 plan of vertebral construction, as shown in the elongated form, and 



* Am. Journ. Sci. vol. xxi. pi. 10. fig. 1 (1881). 



g2 



