84 ANIMAL LIFE PAST AND PRESENT. 



on other inhabitants of the Secondary seas. Curiously 

 enough, in the approximation of the nostrils to the 

 eyes, and also in their sharply pointed teeth, the Fish- 

 Lizards present further resemblances to the Whales, 

 resemblances which we may probably explain by the 

 similar conditions of life of these two widely different 

 groups of animals. 



Before leaving this brief notice of the anatomy of 

 these saurians, a few words must be said as to the 

 structure of the back-bone or vertebral column. It 

 will be seen from Fig. 24 that the whole of this 

 column forms a continuous series, tapering at the two 

 extremities ; and the various segments, or vertebrae, of 

 the different regions of this column are so alike that it 

 requires some practice to distinguish them. As is well 

 known, each vertebral segment in all the vertebrate 

 animals consists of an upper arch enclosing the spinal 

 marrow/and of a lower sub-cylindrical body supporting 

 the arch and underlying the marrow. As a rule, the 

 body and the arch are more or less firmly united 

 together, but in the Fish-Lizards they remain quite 

 separate throughout life. Further, the body of each 

 vertebra (Fig. 24) forms a disk, which is deeply con- 

 cave at the two extremities, like the vertebra of a fish, 

 and quite different from those of most living reptiles, 

 in which the bodies of the vertebrae articulate with one 

 another by a ball-and-socket joint. Another peculiarity 

 of the back-bone of the Fish-Lizards is in the mode of 

 attachment of the ribs. Thus each rib terminates in a 

 fork, of which the two prongs articulate with the two 



