THE BULLFROG 117 



in habit, as are almost all existing hatrachians ; l)ut to 

 which group of the latter can these ancient monsters be 

 considered to have affinity ? It is quite impossible to 

 affirm that they in any way tend to bridge over the 

 chasm which separates the frogs from the efts. They 

 appear, indeed, to have been almost equally removed 

 froni both. It is not impossible that they may find their 

 nearest existing allies among the worm-like Ophiomorpha. 

 There is a curious resemblance between the skulls of 

 these two groups, which also agree in containing more 

 bones than do those of the members of the other two 

 orders. Moreover, some labyrinthodonts appear to have 

 been entirely deprived of limbs. Nevertheless, their 

 largely developed tail constitutes a marked distinction 

 between them and the Ophiomorpha. 



It is somewhat singular that in spite of their predomi- 

 nating aquatic habit all batrachians appear to inhabit 

 fresh water only, and they are thus the only class of 

 backboned animals which have no marine representatives. 

 But as regards the labyrinthodonts, it is very probable 

 that many new and strange forms will come to light, and 

 we look forward with great interest to such a revelation 

 with regard to these air-breathing animals of the carbon- 

 iferous epoch, which, so far as we know, were about the 

 earliest air-breathing vertebrates. We have noted 

 already, in describing the turkey, how different forms 

 of reptilian life preceded and represented the beast life 

 of our own age — its whales, its bats, its cattle, and its 

 beasts of prey. Reptiles represented them during the 

 vast epoch which continued while the secondary rocks 

 were being deposited. The number and variety of 

 labyrinthodonts already found suggests the idea that a 

 great wealth of batrachian life may have preceded and 

 represented the reptile life of the secondary age. They 



