[a]Fig. 7. Semidorsal view of the pectoral girdle and fins
of a Dogfish] (Scyllium canicula) × 2/3.
The gaps between the radiale are blackened.

1. hollow in the mid-ventral part5. propterygium.
of the pectoral girdle which6. propterygial radial.
supports the pericardium.7. meso-pterygial radial.
2. dorsal (scapular portion) of8. meta-pterygial radial.
pectoral girdle.9. outline of the distal part of
3. meta-pterygium.the fin which is supported
4. meso-pterygium.by horny fin-rays.

The meta-pterygium bears about twelve long narrow radials, the first nine of which are traversed by a transverse joint at about two-thirds of the way from their origin. Succeeding the radials are a series of small polygonal pieces of cartilage arranged in one or more rows and attached to the ends of the radials, and finally the fin is completed by the dermal fin-rays.

[a]Fig. 8. Dorsal view of the pelvic girdle and fins of a
male Dogfish] (Scyllium canicula).

1. pelvic girdle.3. clasper.
2. basi-pterygium.4. radiale.

The Pelvic Girdle is much smaller than the pectoral. It is formed of a stout nearly straight bar of cartilage placed transversely across the ventral region of the body. The bar has no dorsal or lateral extensions, and is terminated by short blunt processes. It bears on its posterior surface a pair of facets with which the pelvic fins articulate.

The Pelvic Fin is smaller and more simply constructed than is the pectoral. It consists of a long, somewhat curved rod, the basi-pterygium (fig. 8, 2), running directly backwards on the inner side of the fin, and articulating in front with the pelvic girdle. From its outer side arise a series of about fourteen parallel cartilaginous radials which bear smaller polygonal pieces. The anterior one or two of these radials may articulate independently with the pelvic girdle. In the adult male dogfish the distal end of the basi-pterygium bears a stout rod nearly as long as itself, and grooved on the dorsal surface. This is the skeleton of the clasper (fig. 8, 3).