EXAMPLES OF CONNECTION BETWEEN CLASSES. 



61 



minate over those of the Fish; and the Lepidosiren (Fig. 20), 



in which the characters of the 

 two classes are so completely 

 blended, that Zoologists have 

 not yet agreed on which side 

 it should be placed. Again, 

 the Lizards and Serpents are 

 closely connected with Fishes 

 by two very remarkable ani- 

 mals, not now existing, the 

 Ichthyosaurus (Fig. 21), and 

 the Plesiosaurus (Fig, 22) ; 

 whose remains abound, in cer- 

 tain rocks, to such an extent as to show, that they must have been 



FIG. 20. LKPIDOSIREN. 



FIG. 21. ICHTHYOSAURUS. 



formerly very numerous. On the other hand, there are certain spe- 

 cies of Fishes (which were more numerous and abundant at for- 



Fio. 22 PLESIOSAURUS. 



mer epochs than at present), in whose conformation there is much 

 that reminds us of the Lizards ; very distinct rudiments of lungs 

 being present, and the vertebral column and ribs possessing 

 many characters, in which they resemble those of that order of 

 Reptiles. In the Eels, again, we have the form of the Serpent 



