XIII.] THE FROG. 



a. The fifth digit (that on the outer or ulnar side 

 of the limb) : it presents a cylindrical proximal 

 bone (metacarpal) followed by three others 

 (phalanges), each shorter than its predecessor. 



/3. The fourth digit : a metacarpal bone and three 

 phalanges. 



7. The third digit: a metacarpal bone with two 

 phalanges. 



8. The second digit : a metacarpal bone with two 

 phalanges. 



e. The first digit (pollex) consists only of a small 

 metacarpal bone. 



g. The pelvic girdle. 



a. Its general form : V-shaped, with the apex turned 

 backwards. 



b. The concavity (acetabulum) on each side with 

 which the thigh-bone articulates. 



c. The triradiate fissure running through the aceta- 

 bulum and dividing each half of the pelvis into 

 three pieces, viz. 



a. An anterior elongated piece (ilium) ; subcylin- 

 drical in front, where it articulates with the 

 sacrum ; bearing behind, on its dorsal aspect, a 

 laterally compressed ridge of bone (crista ilii) - 

 it forms almost half of the acetabulum. 



j3. A posterior, irregularly rounded piece (ischium) ; 

 closely united posteriorly with its fellow, in the 

 middle line. 



