232 PALEONTOLOGY. 



begin to sink upon the centrum. There are two distinct sacral 

 vertebras in Nothosaurus. They are known by their long, 

 straight, terminally-bent, and convergent plenrapophyses, the 

 first of which overlaps a little the second. To the convergent 

 ends of these riblets, the ilium (fig. 90, 62, pfy was doubtless 

 ligamentously affixed. In the first caudal vertebra the par- and 

 di-apophyses stand out much farther than in the sacrum ; but 

 rapidly shorten in the second and third caudals. The com- 

 pound process in each supports a short stiliform straight riblet, 

 as in the fifth vertebra of figure 90 ; the anterior and suc- 

 ceeding caudals support hsenial arches and spines, after the 

 disappearance of the pleurapophyses. The haemal arch dis- 

 appears in about the eighth vertebra from the end, and finally 

 the neural arch. The terminal centrums are subelongate and 

 subcompressed. All the centrums have nearly flat articular 

 ends. Both Nothosaurus and Pistosaurus had abdominal ribs, 

 of which the median piece (fig. 90, hs) was sub-symmetrical, 

 the two rays diverging at a very open angle, and terminating 

 in a point or a fork ; the side-pieces (p) seem not to have 

 been so numerous as in Plesiosaurus. 



The scapula (fig. 90, 5 1 ) is a short and strong bone, its 

 blade appearing as a short and narrow sub-compressed process 

 extending from the subquadrate, thick and expanded end, 

 which affords the articular surfaces for the coracoid, clavicle 

 and humerus. 



The clavicle, which is an exogenous process in Plesiosaurus, 

 is here united by a strong oblique suture to the scapula. It 

 expands into, or sends off from its outer part, a broad, flat, 

 obtuse process, near the suture ; then contracts and bends 

 inwards to the episternum, to which it is articulated also by 

 suture. 



The coracoid (fig. 90, 52) sends forward a broad and short 

 flattened process, separated by a narrow notch from the scapular 

 part of its head ; it then contracts and soon expands into a 



