138 



MAEINE EEPTILES OE THE OXEOKD CLAY. 



articular ends of the centra are oval in outline and somewhat deeply concave ; the 

 caudal ribs are strongly developed, but did not help to support the ilium. In the first 

 caudal no chevron-facets are present; these first appear on the second, where, in the 

 type specimen, they are asymmetrically arranged, that on one side being, as usual, on 

 the posterior ventral edge of the centrum, while that on the other is further forwards on 

 the ventral surface : in this vertebra and the next the posterior portion of the centrum 

 is deflected downwards, the tail at this point having apparently curved down from the 

 pelvic region. The neural spines are inclined a little forwards. 



In the rest of the tail (PL VIII. fig*. 4-9 ) the centrum is more or less compressed 

 laterally, especially in its middle portion; the upper and lower borders of the articular 

 faces are flattened, so that in end view the outline of the centrum is somewhat quadrate 



Text-fig. 52. 



Second sacral vertebra of Myctercsuchus nasutvs : A, from belaud ; B, outer end of sacral rib. 



(I?. 3S92, \ nat. size.) 



Jl., flange ou ou'er end of sacral rib ; U.S., surface for ilium ; n.c, neural canal; 



n„i_p., neural spine ; p.z., posterior zvgapophysis. 



(PI. VIII. figs. 5 a, 6 a), the sides being convex; the chevron-facets are borne at the 

 hinder end of a pair of ridges which run nearly the whole length of the ventral surface 

 of the centrum and are separated by a narrow fiat or concave band of bone. 



The neural spines are peculiar, and differ considerably from those of the Steneesaurs 

 described above. In the most anterior caudals, as above noted, the spine slopes a 

 little forwards and is thickened at its upper end. Further back in the series (at 

 about the sixth) it becomes upright, and behind this slopes backwards. Here it is a 

 bioad thin plate of bone extending nearlv the whole length of the arch. At about 



