78 THE CRUISE OP THE BETSEY ; OB, 



in the others both centrum and process seemed anchylosed, 

 as in quadrupeds, into one bone ; and there remained no scar 

 to show that the suture had ever existed. In some specimens 

 the ribs seem to have been articulated to the sides of the 

 centrum ; in others there is a transverse process, but no marks 

 of articulation. Some of the vertebrae are evidently dorsal, 

 some cervical, one apparently caudal ; and almost all agree in 

 showing in front two little eyelets, to which the great de- 

 scending artery seems to have sent out blood-vessels in pairs. 

 The more entire ribs I was lucky enough to disinter have, as 

 in those of crocodileans, double heads ; and a part of a fibula, 

 about four inches in length, seems also to belong to this ancient 

 family. A large proportion of the other bones are evidently 

 Plesiosaurian. I found the head of the flat humerus so cha- 

 racteristic of the extinct order to which the Plesiosaurus has 

 been assigned, and two digital bones of the paddle, that, from 

 their comparatively slender and slightly curved form, so un- 

 like the digitals of its cogener the Ichthyosaurus, could have 

 belonged evidently to no other reptile. I observed, too, in 

 the slightly-curved articulations of not a few of the vertebra?, 

 the gentle convexity in the concave centre, which, if not 

 peculiar to the Plesiosaurus, is at least held to distinguish it 

 from most of its contemporaries. Among the various non- 

 descript organisms of the shale, I laid open a smooth angu- 

 lar bone, hollowed something like a grocer's scoop ; a three- 

 pronged caltrop-looking bone, that seems to have formed 

 part of a pelvic arch ; another angular bone, much massier 

 than the first, regarding the probable position of which I could 

 not form a conjecture, but which some of my geological friends 

 deem cerebral ; an extremely dense bone, imperfect at each 

 end, which presents the appearance of a cylinder slightly 

 flattened ; and various curious fragments, which, with what 

 our Scotch museums have not yet acquired, entire reptilian 

 fossils for the purposes of comparison, might, I doubt not, be 



