STENEOSAUEUS. 



105 



met with elsewhere in the group. Usually the anterior caudals bear fused caudal 

 ribs, which seem to have united either entirely with the neural arch or perhaps to a 

 small extent with the centrum ; the first two or three are somewhat thickened, but 

 further back they become strongly compressed from above downwards and seem to 

 have curved a little downwards at their outer ends. 



The chevrons (text-fig. 40) begin two or three vertebras behind the sacrum. They 

 articulate between the centra, but the facet (_/'.) for the posterior end of the centrum 

 is much better developed than that for the anterior end of the succeeding centrum. 

 The chevrons vary very much in form in the different parts of the tail. Judging from 

 some bones preserved with one of the skeletons, it appears that in a few of 

 the more anterior vertebra? the two arms of the chevrons remained separate, not 

 uniting below to produce the Y-shaped bone, the form in which they appear in the 

 greater part of the tail. In the anterior of these Y-shaped chevrons (text-fig. 40, A, P» ) 



Text- fig. 40. 



Chevrons of Steneosaurus leedsi : A, anterior chevron from side ; B, anterior chevron from front • C. middle 

 chevron from side ; D, posterior chevron from front ; E, posterior chevron from side. (B. 3S06. 

 | nat. size.) 



/., facet for union with the caudal centra. 



the leg of the Y is long and fairly stout; the arms of the Y terminate above in an 

 oblique convex facet, in front of and behind which there is a small prominence. 

 Further back the lower arm of the Y is shorter and more compressed laterally 

 (text-fig. 40, C). In the posterior chevrons (text-fig. 40, D, E) also the ventral arm is 

 greatly compressed and at the same time elongated, so that it extends considerablv 

 both in front of and behind the supporting arms, thus giving the bone, as seen from 

 the side, the form of an axe-head : this form of chevron seems to have continued 

 backwards to within a few vertebree of the end of the tail. 



Shoulder-girdle and Fore Limb (text-figs. 41-42). — The shoulder-girdle (text-fig. 41) 

 does not differ in any important character from that of the recent Crocodiles. It 



PART II. p 



