WEALDEN CROCODILES. 425 



extends along the middle of the under part of the transverse process, until it is finally 

 lost near the extremity of the process, which here has exchanged its lamellar for a 

 prismatic form, terminating in the obtuse extremity against which the tubercle of the 

 rib abutted. The supporting bracket is not quite vertical, but inclines a little forward, 

 and behind it there is a deep, angular fossa. The posterior zygapophyses (figs. 4, 5, 

 b,b) diverge from each other and from the neural arch immediately above the poste- 

 rior extremity of the spinal canal ; each articular surface, which is directed downward 

 and outward, forms, as it were, the base of a posterior root of the spinous process, 

 which is convex externally, diminishing in breadth as it converges to meet its fellow 

 at a very acute angle above a deep fissure extending forwards into the substance of 

 the base of the spine, similarly to the fissure before described as extending backward 

 from the opposite part of the spine into its substance. As far as I could detach the 

 matrix, these fissures extended so that they seem to communicate, and the neural arch 

 to be perforated by two longitudinal passages, one for the spinal cord, and the other, 

 running above and parallel with the former, through the base of the spinous process. 



The anterior parts of each spinal plate are thickened and rounded, like those 

 behind, and extend to the origins of the anterior zygapophyses. The diameter of 

 this remarkable spinal fissure is from 4 to 3 lines. It does not exist in the vertebrae 

 of the Iguandon, Megalosaurus, or other Dinosauria. 



The base of the spinous process in this (presumed) Poilcilopleuron's vertebra, 

 instead of descending from behind forward in a graceful curve, as in the Dinosaurs, 

 forms a straight and almost horizontal line, 3 inches in extent ; the spine maintains 

 the same breadth to its summit, which is truncated rather obliquely ; its height is 

 4 inches 9 lines, measured from the upper end of the posterior zygapophyses ; it is 

 thickened and rounded at its truncate summit. The height of the spine of a corre- 

 sponding vertebra of the Iguanodon, with a centrum of the same length, is 9 inches. 

 Thus the present vertebra more resembles, in the form and proportions of its spinous 

 process, as in other characters, the vertebra3 of the Crocodilians. 



The posterior part of the neural arch, with the spinous process of the vertebra, 

 here described, is figured in Mantell's ' Illustrations of the Geology of Sussex,' p. xii, 

 fig. 1, as the "Lumbar Vertebra of the Iguanodon." It is not, however, a lumbar 

 vertebra nor a part of the Iffuanodon ; if it does not belong to the Poikilopleuron, it 

 indicates an unknown genus of Crocodilians. 



Nos. /2V4 ^nd -^2^, in the Mantellian Collection, are the two moieties of a fossil 

 caudal vertebra, fractured obliquely across the middle of the body, the length of 

 which is to the breadth of its articular extremity as 3 to 2 ; both extremities are 

 slightly concave ; the body is gradually contracted from the t\\ extremities towards 

 the middle part ; bears a transverse process developed from the posterior and upper 

 part of its side, behind which there is a shallow groove ; has tlie neural arch anchy- 

 losed, without trace of suture, to nearly the whole of the longitudinal extent of its 



