﻿LIASSIC FORMATIONS. 



21 



mcntous attachments of the vertebrae and of their elements, they have yielded to 

 external pressure or movement of the matrix, and have rotated on their axis — some 

 of the Long-spined vertebrae to the right, some to the left — with a slight displacement 

 of the longer ribs from their attachments. 



The third cervical vertebra is displaced about three inches below the axis and 

 atlas, which remain in connection with the occipital tubercles, the third to the 

 fifteenth cervicals are prone with the spines uppermost, and the pleurapophyscs in 

 natural connection with the sides of the centrum, the lower part of which is buried 

 in the matrix. Except a slight dislocation between the seventh and eighth, these 

 cervicals have retained their natural sequence and relative position. As the spines 

 grew longer and larger they offered a surface upon which the superincumbent 

 pressure could operate, so as to rotate the vertebras sideways ; and from the sixteenth 

 to the twenty-eighth inclusive, they are turned half round, with the spines downward 

 or to the left ; but all these vertebras retain their natural mutual connections. The 

 twenty-ninth vertebra is dislocated, exposing the anterior articular surface of the 

 centrum ; the thirtieth has suffered fracture of its spine ; the thirty-first and thirty- 

 second are partly bent to the left ; the thirty-third and thirty-fourth are turned with 

 the spines to the right side ; that of the thirty-fifth is broken from its neural arch ; 

 the thirty-sixth to the forty-eighth vertebras have the neural spines turned to the right, 

 retaining almost their natural relative positions. The forty-ninth vertebra has kept 

 the original prone position, as when imbedded ; the next ten show the side view, with 

 the neural spines to the right; the sixty-first to the sixty-fifth are prone, but with a 

 slight deviation of the neural spines, some to the right, some to the left ; the next six 

 vertebras have yielded in the opposite direction ; there is then a deeper space, equal 

 to the extent of five vertebras, in which there are the centrums of three vertebras and 

 some hasm apophyses irregularly scattered. Beyond this part the terminal caudal 

 vertebras resume their position and natural connections, and are preserved, seven in 

 number, to the last. The antecedent exceptional violence shown in the caudal series 

 has probably been due to the tugging and gnawing of some predatory animal, whilst 

 this part of the dead and partly decomposed Plesiosaur continued to be exposed at the 

 sea-bottom. 



The scapulas (51) and articular ends of the coracoids (52) appear parallel with the 

 twenty-fifth to the twenty-seventh vertebras, the left being rather further back than 

 the right. Both humeri (53) have been dislocated at the shoulder-joint by super- 

 incumbent pressure, and the articular ends of the scapulas overlap their heads. The 

 rest of the bones of the pectoral fins have retained their natural relative position, 

 protected by the tough, closely-fitting dermal sheath, until this slowly dissolved away. 

 The iliac bones (62) lie by the sides of the forty-seventh to the fiftieth vertebras, 

 almost in the axis of the spine, with their proximal ends turned backward, and their 

 acetabular end forward, having become detached from the thick, converging pleura- 



