52 THE ELASMOBRANCH FISHES 



fin (see fig. 53) are an integral part of the axial skeleton, being the prolonga- 

 tions of haemal spines under the haemal arches (h.a.). These consist of a series 

 of rays, two of which correspond to a segment. The dorsal lobe of the fin is also 

 supported by rays which begin back of the segment shown in figure 53. These 

 dorsal rays are more than twice as numerous as the segments present. 



ANAL FIN 



The base of the anal fin {Ic, fig. 57) ends anteriorly at about the fifty-third 

 centrum of the spinal column. The basal piece, barring the fact that it is seg- 

 mented in front, is remarkably similar to that of the dorsal. From it, however, 

 the radials {ra.) proceed in a less definite fashion. 



