426 



THE DOGFISH 



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 together at their bases to form 

 basal cartilages which articulate with the corresponding 

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

 pelvic arch (Fig. 105, BP) is a transverse bar of cartilage 

 situated just in front of the vent, and representing the pubic 

 and ischiatic portions of the girdle in the frog, an iliac 

 region, extending dorsally, and coming into connection 



Rad 



Fig. 105. — Diagram of the Eiasmobranch pelvic arch (B P, Cep, PP, Sy) and fin. 

 Bas. basal cartilage ; Fo'. ne^ve foramen ; /. iliac process ; Pru. anterior ray 

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

 Wiedersheim.) 



with the vertebral column, being hardly represented. 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. 417) is connected with the distal end of the 

 basal cartilage. 



The shoulder-girdle (Fig. 106) is a strong inverted 

 arch of cartilage situated just behind the last branchial 



