72 THE COMMON FROG. [chap. 



though not quite universal, since the bony pike 

 {Lepidosteiis) has a ball at one end of each vertebra 

 and a cup at the other. Moreover, even in some 

 reptiles [e.g. the lizards called Geckoes) the vertebrae 

 are biconcave, and the same was the case with the 

 majority of those species of crocodiles the remains of 

 which are found in strata older than the chalk, and 

 even in existing crocodiles the first vertebra of the 

 tail is biconcave. 



Vertebrae with a cavity in front of the centrum and 

 a ball behind it are found in the crocodiles now living 

 as well as in the frog, while vertebrae with a ball in 

 front and a concavity behind are found even amongst 

 beasts as in the joints of the neck of Ruminants, e.g. 

 the sheep. Thus though the vertebrae of the frog's 

 class exhibit no very decided signs of affinity, they 

 show more resemblance to those of fishes than to 

 those of any other non-batrachian class. 



The transverse processes of the ninth or last ver- 

 tebra in front of the coccyx, articulate with the 

 haunch bones, but are not very remarkable in shape. 

 In some frogs and toads the transverse processes of 

 this vertebra become enormously expanded, and the 

 expanded or non-expanded condition of this part is 



Fig. 36.— Anterior aspect of Coccyx, showing the double articular concavities placed 

 side by side beneath the neural arch. 



a character made use of in zoological classification. 

 The coccyx is made up mainly, as has been said, of 



