Manchester Memoirs, Vol. liv. (1909), No. 4. 5 



6. The fact that the caudals retain a long rib tightly 

 fused on down to the end of the tail, showing that there 

 can have only been a very small fin, if any. 



I shall discuss some interesting mechanical considera- 

 tions presented by resemblances between the pectorals 

 and sacrals in a complete osteology of the species. 



Pectoral Girdle. 



The Manchester Museum specimen, L. 7077, has a 

 beautifully exposed pectoral girdle lacking only part of 

 the right scapula and clavicle. The general plan of the 

 girdle is that of the genus Cryptocleidus. 



Coracoids. The coracoids are not completely exposed, 

 and the shape of the postero-lateral angles is not shown. 



The two coracoids meet in a very long symphysis. 

 This is usually only about a centimetre deep, but between 

 the glenoid ends becomes very thick, probably at least 

 six centimetres. As the lower surface forms a uniform 

 curve, this implies a great depression of the visceral 

 surface of the coracoids behind the inter-glenoid bar. 



The glenoid part of the coracoid is about six centi- 

 metres deep : the facet for the scapula is seven centimetres 

 long, that for the head of the humerus being only five 

 centimetres. 



The position of the right coracoid with regard to the 

 undisturbed dorsal vertebrae shows that it cannot have 

 the postero-lateral corner extended into a process similar 

 to that of Cryptocleidus, the width of the lower end given 

 in the figure is, in fact, the maximum possible. 



Scapula. The scapula is a triradiate bone, the 

 posterior ramus of which articulates with the coracoid 

 and forms part of the glenoid cavity. This ramus is 

 triangular in transverse section, the upper surface being 

 flat, and, where it joins the dorsal ramus, six centimetres 



