88 TYPES OF ANIMAL LIFE 



Such, then, is the turkey in itself, a member of the 

 gallinaceous order, and such are the structural characters 

 it shares with other birds. It now only remains to point 

 out the leading characters whereby it, with the other 

 members of its class, differs from creatures which are 

 not birds. The class of birds, as one of the classes of 

 back-boned animals, stands between the class of beasts 

 on the one hand and the class of reptiles on the other. 



We saw, when considering the opossum, that the class 

 of beasts is divided into a number of very different 

 orders. How greatly these differ from one another will 

 be apparent if we recall to mind the obvious dissimi- 

 larity which exists between an ape and an ox, a bat and 

 a lion, a mole and a squirrel, a seal and a mouse, an 

 elephant and an armadillo, or an antelope and a whale ; 

 and yet these are all of them beasts. We also saw how 

 great a diversity may exist in a single order of beasts 

 such as that, e.g., to which the opossum belongs. 



Not less striking are the contrasts and divergences 

 which exist among the various kinds of reptiles, such as 

 between serpents and alligators or between terrapins and 

 lizards. 



If, however, we take into account the forms of reptilian 

 life which have passed away since the deposition of the 

 chalk cliffs of the English coast since, that is, the end 

 of the secondary period the contrasts and divergences 

 become yet more striking. 



In those early times, instead of porpoises and whales, 

 the sea swarmed with reptilian predecessors of those 

 short-necked beasts. It swarmed with ichthyosauri, 

 often of great bulk, and also abounded with those large 

 aquatic creatures with more than swan-like necks, the 

 plesiosauri. Huge reptiles also grazed in the then exist- 

 ing fields or fed on the leaves, fruit, and twigs of forests. 



