228 PALAEONTOLOGY. 



The mouth was wide, and the jaws long, and armed with 

 numerous pointed teeth, indicative of a predatory and carni- 

 vorous nature in all the species ; but these differed from one 

 another in regard to the relative strength of the jaws, and the 

 relative size and length of the teeth. 



Masses of masticated bones and scales of extinct fishes, 

 that lived in the same seas and at the same period as the 

 Ichthyosaurus, have been found under the ribs of fossil speci- 

 mens, in the situation where the stomach of the animal was 

 placed; smaller,' harder, and more digested masses, containing 

 also fish-bones and scales, have been found, bearing the impres- 

 sion of the structure of the internal surface of the intestine of 

 the great predatory sea-lizard. One of these " coprolites" is 

 figured beneath the skeleton in fig. 89. 



In tracing the evidence of creative power from the earlier 

 to the later formations of the earth's crust, remains of the 

 Ichthyosaurus are first found in the lower lias, and occur more 

 or less abundantly through all the superincumbent marine 

 strata, up to, and inclusive of, the chalk formations. They are 

 most numerous in the lias and oolites, and the largest and 

 most characteristic species have been found in these forma- 

 tions. More than thirty species of Ichthyosaurus are known 

 to the writer, many of which have been described or defined. 



"Whenever the antecedent forms of an extinct genus of any 

 class are known, the characters of such genus should be com- 

 pared with those of its predecessors in such class, rather than 

 with its successors or with existing forms, in order to gain an 

 insight into its true affinities. 



We derive a truer conception of the affinities of the Ich- 

 thyosaurus by comparison with the triassic Labyrinthodonts, 

 as we do of the Plesiosaurus by comparison with the muschel- 

 kalk Sauropterygians, than of either by comparison with 

 modern Lacertians and Crocodilians. It is commonly said that 

 the Ichthyo- or the Plesiosaurus resembles the lizards more. 



