CLASS AMPHIBIA 



543 



lumbar vein is often quite large, with branches running the entire 

 leng-th of the body cavity and others coming from the lateral muscles. 



Skeleton and Muscles 



The pectoral girdle of the toad is quite different from that of the 

 bullfrog and leopard frog. In the latter specimens, the two halves 

 of the girdle grow together in the midventral line, separated by a 

 cartilage, and the chest is not expansible. This type of pectoral 

 girdle is known as firmisternal. In the toad, however, the epicoracoid 

 cartilages separating the two halves of the girdle overlap in front, 

 and the chest is expansible. This type of pectoral girdle is known 

 as arciferal (Fig. 293). 



2 jy? vertebra 



Sacral 



diapopbjses 



dilated 



Ilium 



' Urostyle 



Ij- Ischium 



Fig. 294. — Pelvic girdle and urostyle of the common toad, Bufo americamis. 



As in the bullfrog, the toad has nine typical vertebrae and a tenth 

 which is included in the urostyle. Like the frog's, the vertebrae 

 are procoelous. Unlike that of the frog, however, the single sacral 

 vertebra which precedes the urostyle has its transverse processes 

 (sacral diapophyses) dilated or expanded. In the bullfrog they were 

 more circular. 



The muscles of the legs, pectoral girdle, and body wall are large 

 and thick. In preserved specimens their origins are clearly out- 

 lined, and they are more easily separated one from another in dis- 

 section than those of the leopard frog. 



Nervous System and Sense Organs 



The large calcareous bodies around the spinal ganglia, seen in the 

 bullfrog, are not evident in the toad. While both bullfrogs and 



