442 



THE DOGFISH 



CHAP. 



are supported by a double series of delicate horn-like fibres, 

 the dermal fin-rays. 



The paired fins are also supported proximally by cartila- 

 ginous 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 repre- 

 senting the pubic and ischiatic portions of the girdle in the 



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

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

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

 Wiedersheim's Comp. Anatomy.} 



frog (p. 50), an iliac region, extending dorsally, and coining 

 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 

 arch of cartilage situated just behind the last branchial 



