. The elasmobranch fishes. Chondrichthyes. THE ELASMOBRANCH FISHES 95 from tlie basal and radial cartilages, and extend outward to be attached to the connective sbeath of the ventral side of the fin. The muscles governing the clas])ers of the fins in the male are in bundles specialized from dorsal and ventral radial mus- cles. We may first examine them on the dorsal side of the pelvic of the male (fig. 96). Here they are continued from the myomeres to the fin, parallel with the radials, and are firmly attached to the pe- ripheral part of the fin skeleton. The first of these muscles is the addu
. The elasmobranch fishes. Chondrichthyes. THE ELASMOBRANCH FISHES 95 from tlie basal and radial cartilages, and extend outward to be attached to the connective sbeath of the ventral side of the fin. The muscles governing the clas])ers of the fins in the male are in bundles specialized from dorsal and ventral radial mus- cles. We may first examine them on the dorsal side of the pelvic of the male (fig. 96). Here they are continued from the myomeres to the fin, parallel with the radials, and are firmly attached to the pe- ripheral part of the fin skeleton. The first of these muscles is the adductor (ad.), which arises from the posterior border of the pelvic girdle and is inserted on the distal end of the basipterygium (see p. 50, fig. 55b, ). The external flexor muscle , fig. 96), which has its origin along the inner margin of the basipterygium {), is inserted on the "beta" cartilage (B, fig. 55b). In Heptanchus the internal flexor () arises in common with, but deeper than the external flexor on the basipteryginm and on the "beta" cartilage and is inserted on the segment 6- (fig. 55) and on the proximal part of the basal cartilage (ba.). On the dorsal side are also to be seen the dilator (dl.) and the compressor (cp.) muscles. The dilator arises on the proximal end of the basal cartilage (ha.) and is inserted distally with the connective tissue covering the tip of the basal cartilage. The compressor muscle (cp.) has its origin from the "beta" cartilage (/8, fig. 55b) , and passes backward and outward to be inserted on the last radial car- tilage. One of the muscles associated with the clasper, which is not seen in dorsal view, is the constrictor of the sac. Its fibers arise from the seg- ments &.^"-, and from the proximal end of the basal cartilage. Its dorsal fibers are inserted on the curved radial and its ventral fibers form the wall of the pterygopodial Fig. 96. Muscles of the pelvic fin of male, Hep
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