THE PECTORAL FIN articulates with the pectoral girdle by means of three basalia or basal cartilages, the =propterygium=, =meso pterygium= and =meta-pterygium=. The most anterior and the smallest of these is the =propterygium= (fig. 7, 5), while the most posterior one, the =meta-pterygium= (fig. 7, 3), is much the largest. Along the outer borders of the three basalia are arranged a series of close set cartilaginous pieces, the =radiale=. The propterygium supports only a single radial, which is however much larger than any of the others. The meso-pterygium also supports only a single radial which divides distally. [Illustration 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 part of the pectoral girdle which supports the pericardium. 2. dorsal (scapular portion) of pectoral girdle. 3. meta-pterygium. 4. meso-pterygium. 5. propterygium. 6. propterygial radial. 7. meso-pterygial radial. 8. meta-pterygial radial. 9. outline of the distal part of the fin which is supported 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. [Illustration FIG. 8. DORSAL VIEW OF THE PELVIC GIRDLE AND FINS OF A MALE DOGFISH (_Scyllium canicula_). 1. pelvic girdle. 2. basi-pterygium. 3. clasper. 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). FOOTNOTE: [34] See Marshall and Hurst's _Practical Zoology_, 4th ed. London, 1895, p. 214. CHAPTER VII. THE SKELETON OF THE CODFISH. (_Gadus morrhua._) I. EXOSKELETON. The exoskeleton includes