ZUULUGY 



SECT. 



ends of which arc articulated with stout cartilages (Bas), often 

 replaced by bones, the hasalut, which serve to strengthen the tin at 

 its point of union with the trunk. 



In all classes above Fishes the paired fins are, as we have seen, 

 replaced by five-toed or pentadadyle limbs. These are supported by 

 bones, probably to bo looked uponas greatly modified pterj'giophores, 



Fig. 7(5(5. — Diagi-am of tbiee .stages in the developmi-'nt of the pelvic fins. In A the anterior 

 pterygiophores on the right side (Rwl), have united to form a basal cartilage (Bus.) : in B the 

 basalia (Hatt.) are fuUj' formed and are uniting at * to form the i)elvic girdle ; in C the pelvic 

 girdle (G) is fullj- constituted, and at t has segmented from the basale ou the right side. 

 CI. cloacal aperture. (Fi-om Wiedersheim's Comjiaratioc Anatomy.) 



\ 



and obviously homologous in the fore- and hind-limbs. In the proxi- 

 mal division of each limb there is a single rod-like bone, the humerus 

 (Fig. 767, HU), or upper-arm-bone, in the fore-limb, the femur 

 (Fig. 7(J8, FE,) or thigh-bone, in the hind-limb. In the middle 

 division there are two elongated bones, an anterior, the radius 

 (RA), and a posterior, the ulna (UL), in the fore-limb ; an anterior, 

 the tibia (TI), and a posterior, the fibula (FI), in the hind-limb. 

 Next follow the bones of the hand and foot, Avhich are again 

 divisible into three sets : earjxds or wrist-bones, metacarpals 



