162 



COMPARATIVE ANATOMY 



shank, are also exceedingly long, in correlation with the mode of 

 progression of these animals. The skeleton of the extremities 

 is more strongly ossified in Anurans than in Urodeles, in which 

 many of the elements remain cartilaginous. 



Traces of an extra element ("prcJiallux") occur on the tibial 

 side of the tarsus, and in both Urodeles and Anurans indications 



Groove be- 

 tween radius 

 and ulna 



Ulna 



Ulnare 



TUbialt 



Tarsale II and III 

 Tar sale I 



Central* 



Prehallux 



Carpal 

 III" 



FIG. 124. A, RIGHT FORE-ARM AND HAND, AND B, RIGHT FOOT, OF 

 Rana esculenta. From the dorsal side, x 2. After E. Gaupp. 



of an additional pre-axial ray in the manus are occasionally met 

 with. The number of phalanges in the individual digits varies in 

 different Amphibians. 



Vestiges of the extremities can be recognised externally in 

 embryos of the limbless Gymnophiona. 



