﻿KIMMERIDGE CLAY. 



97 



the spine of Omosaurus has been attached, in the tarsal spine of the Platypus (Ornit/io- 

 rhynchus paradoxus, Plate XXIII, fig. 2, twice natural size). There was the same 

 proportion of breadth to the body of the spine ; the same sudden expansion to form the 

 base ; the same medial rising in the long axis of the base, and furrows extending 

 therefrom to the margin. But these radiating furrows are more numerous, and the spine, 

 though it is hollow as in Omosaurus, has that cavity converted by terminal apertures into 

 a canal, and this canal is traversed, as in the poison-fang of certain Ophidian Reptiles, by 

 the duct of a gland. The affinity shown by the Monotrematous Mammals to the Beptilia 

 in certain parts of the skeleton is well known, and is closer in the structure of sternum, 

 coracoids, and clavicles, than in any Bird. 



