80 



THE ELASMOBKANCH FISHES 



a great deal in the direction which it takes. In Heptanchiis it slopes very 

 obliquely backward, while in Heterodontus and especially in the rays it stands 

 more nearly vertical. In general it is capped by a snprascaj)ular cartilage. 



Fig. 86. Pelvic fin and girdle of male. A. Heterodontus francisci. B. Bhinobatis prodvctus. 

 (Chester Stock, orig.) 



j3, beta cartilage; 6.^"", intermediate segments; ia., basal or axial cartilage; ba.p., basip- 

 terygium; d.mg. and mg. (fig. 85), dorsal marginal; d.tr}-", first and second dorsal termi- 

 nal cartilages; pi., pelvic cartilage; ra. (fig. 85), radials; spn., spine; tr.^, accessory termi- 

 nal; v.tr., ventral terminal. 



Near the union of the coracoid and scapular pieces, but on the coracoid, is 

 the articular process. This area of articulation in the sharks is directed verti- 

 cally or obliquely and consequently is usually composed of two convex sur- 

 faces {Squatina) . The surface in the rays differs from that in the sharks in 

 that it is longitudinal in position and much greater in extent. Torpedo (fig. 

 84b) has a type of articulation intermediate between sharks and rays. 



