LIMBS AND GIRDLES. 



437 



Gegenbaur, the pectoral and pelvic girdles are homologous 

 with branchial arches, while the primitive limbs are made 

 up of modified fin rays originally like those of the unpaired 

 fins. According to Dohrn, the limbs are residues of a 

 longitudinal series of segmentally arranged outgrowths, 



Figs. 185 and 186. — Ideal fore- and hind-limb. — After Gegenbaur. 



H., Humerus ; R., radius ; U., ulna ; r'., radiale ; «'., ulnare ; ?., 

 intermedium ; c, centrale ; 1-5, carpalia bearing the correspond- 

 ing digits with metacarpals («zc) and phalanges (ph.). 

 / , Femur ; ii. t tibia \Ji., fibula ; z\, intermedium ; t., tibiale (astra- 

 gatus);/., fibu\are(flsca/a's); c. , centrale; 1-5, tarsalia bearing the 

 corresponding digits with metatarsals (tut.) and phalanges (J>h.). 



perhaps comparable to the parapodia of an Annelid. 

 According to Wiedersheim, the girdle portion is primarily 

 due to the centripetal growth of the fin skeleton, which 

 arose from a localisation of the supports of continuous 

 lateral folds. 



The pectoral or shoulder girdle consists of a dorsal 

 scapular portion or shoulder - blade, a ventral coracoid 



