442 



THE DOGFISH 



CHAP. 



phores, the proximal ends of which are more or less fused 

 together to form basal cartilages or basalia. The free 

 edges of the fins are supported by a double series of 

 delicate horn-like fibres, the dermal fin-rays. 



The paired fins are also supported proximally by 

 cartilaginous pterygiophores, fused at the bases to form 

 basal cartilages which articulate with the corresponding 

 arch or girdle, and distally by horny, dermal fin-rays 

 (Fig. 115, d. f. r). The pelvic arch (Fig. 114, BP) is a 

 transverse bar of cartilage situated just in front of the 

 vent, and representing the pubic and ischiatic portions 



FIG. 114. Diagram of the Elasmobranch pelvic arch (BP) and fin. 

 Bus. basal cartilage ; Fo'. nerve-foramen ; /. iliac process ; Pro. anterior ray 

 articulating directly with the arch ; Rod. the remaining radial cartilages. (From 

 Wiedersheim's Comparative Anatomy.) 



of the girdle in the frog (p. 50) ; an iliac region, extending 

 dorsally, and coming into connection with the vertebral 

 column, being hardly represented (I). On its posterior 

 edge are articular facets for the pelvic fins, each of 

 which has a single very large basal cartilage (Bas), but 

 one or two of the anterior rays (Pro) may articulate 

 separately with the arch. In the male, the skeleton of 

 the clasper (p. 433) is connected with the distal end of 

 the basal cartilage. 



The shoulder-girdle (Fig. 115) is a strong, inverted 



