326 



LOWER VERTEBRATES. 



pouch secrete the necessary additional quantity to supply all that is required for 

 ■development. In so far as observation has extended, this is a solitary instance among 

 Batrachians, in which the embryo is nourished at the expense of the materials derived 

 from the parent." 



The family Xenotpodid^ agrees with the Pipidoe in all important respects, as the 

 structure of the skull, the scapular arch, coossification of sacrum and coccyx, etc. (Fig. 

 192), but differs in the presence of teeth in the upper jaw. It includes but the single 

 genus -ZenopMS, which is represented by three species of the Ethiopian realm. Its toes 

 are acute, and the feet are broadly webbed for aquatic life. There is a short tentacle 

 below the eye. This is a remnant of the balancer, which characterizes the larvae. 

 These creatures have, on each side of the head, a long tentacle extending backwards, 

 giving them very much the appearance of a siluroid or cat-fish. The species are of 

 plain colors. 



Sttb-Oeder II. — Aecipera. 



The Anuraof this division fall into nine families, which differ in simple and gener- 

 ally obvious characters. Thus the Bufonidae and Dendrophryniscidaj have no 

 teeth whatever, and the former family, which includes the true toads, differs from the 



Fig. 194. — Skeleton of Ccratophrys dorsata. 



latter in having the transverse processes of the sacrum much expanded and flattened 

 (Fig. 192), as distinguished from the subcylindric form seen in the Dendrophryniscidse. 

 This difference separates several other families also. Five of the remaining families 

 have teeth in the upper jaw only. In one of these, the Cystignathidse, the sacral transverse 

 processes are cylindric. Fig. 194, and in the four others they are expanded. Two of 

 these differ much from the other two in having the ball and socket of its vertebrae 

 related in a way the reverse of what is seen in all other members of the order, but 

 similar to the structure found in many of the salamanders. That is, the ball is in 



