ICHTHYOSAURUS. 133 



SECTION IV. 



ICHTHYOSAURUS. 



Nearly at the head of the surprising discoveries, which 

 have been made relating to the family of Saurians, we may 

 rank the remains of many extraordinary species, which 

 inhabited the sea; and which present almost incredible 

 combinations of form, and structure; adapting them for 

 modes of Ufe that do not occur among living reptiles. These 

 remains are most abundant throughout the lias and oolite 

 formations of the secondary series.* In these deposites we 

 find not only animals aUied to Crocodiles, and nearly ap- 

 proaching to the Gavial of the Ganges ; but also still more 

 numerous gigantic Lizards, that inhabited the then existing 

 seas and estuaries. 



Some of the most remarkable of these reptiles have been 

 arranged under the genus Ichthyosaurus, (or Fish T-izard,) 

 in consequence of the partial resemblance of their vertebrae 

 to those of fishes. (See Plate 1, Fig. 51, and Plates 7, 8, 9.) 

 If we examine these creatures with a view to their capa- 

 bilities of locomotion, and the means of offence and defence 

 which their extraordinary structure aflforded to them ; we 

 shall find combinations of form and mechanical contrivances 



* The chief repository in which these animals have been found is the 

 lias, at Lyme Regis ; but they abound also along the whole extent of this 

 formation throughout England, e. g. from the coast of Dorset, through 

 Somerset and Leicestershire, to the coast of Yorkshire : they are found 

 also in the lias of Germany and France. The range of the genus Ich- 

 thyosaurus seems to have begun with the Muschelkalk, and to have ex- 

 tended through the whole of the oolitic period into the cretaceous for- 

 mation. The most recent stratum in which any remains of this genus 

 have yet been found is the chalk marl at Dover, where they have been 

 discovered by Mr. Mantell : I have found them in the gault, near Benson, 

 Oxon. 



VOL. I. 12 



