574 



THE WONDERS OF GEOLOGY. 



Lect. V. 



are large, and in some species consist of one hundred 

 bones ; the hinder pats are smaller, and contain but thirty 

 or forty (Lign. 128). The internal structure of these instru- 

 ments therefore resembles that of the paws of turtles ; and (as 

 is even the case in the fin of the Porpoise) the same elements 

 of an arm are found as in the mammalia, viz. a humerus, 

 radius, ulna, and phalanges. The nostrils, which in Croco- 



1. 



Lign. 1 2 S . — Paddles of the Ichthyosaurus and Plesiosaurus, in lias 



SHALE, FROM LYME REGIS. 



Fig. 1 . Left fore-paddle of the Ichthyosaurus. 

 Fig. 2. Left fore-padd]e of the Plesiosaurus. 



{One eighth the natural iize.) 



diles are situated at the extremity of the beak or muzzle, 

 are placed, as in the cetacea, beneath the orbits. The 

 vertebrae are hour-glass shaped, like those of the sharks and 

 other fishes ; the spinal column, therefore, admitted of the 

 utmost freedom of motion ; while in the neck, the vertebrae 

 connecting the head to the spine column are anchylosed, 



