PECTORAL GIRDLE AND FIN. Remove from the body the pectoral girdle, with the fins attached, and carefully scrape off the muscles from the cartilaginous parts. It will be found that the support of the fin is partly of cartilaginous plates and rods, partly of horny fibres (_dermal fin-rays_) which overlie the extremities of the cartilages and extend to the edges of the fin. These fibres are in two layers, one beneath the skin of each side. They are formed in the dermis. A similar arrangement of horny fibres is found in all the other fins. The pectoral girdle passes across the ventral surface of the body and upward on each side to the level of the vertebral column. The stout ventral bar presents numerous facets for the origin and insertion of muscles. The articular surfaces for the pectoral fins are well up on the sides of the girdle. The slender dorsal end of each side of the girdle consists of a separate bar of cartilage, movably articulated to the lower portion. The ascending limb of the girdle, from the fin articulations to the base of the cartilage just mentioned, is called the _scapular portion_; the small bar is the _supra-scapular_; the ventral bar between the fin articulations is the _coracoid portion_. The cartilaginous skeleton of the pectoral fin consists primarily of a row of three _basal_ cartilages, all articulating proximally with the girdle. The middle basal is much the largest. Distal to the basals are three rows of rod-like _radial_ cartilages, the proximal row being articulated to the basals. PELVIC GIRDLE AND FIN. Remove the pelvic girdle from the body with the pelvic fins attached, and clean away the muscles. The pelvic girdle consists of an almost straight bar of cartilage, slightly thicker at its middle than at its ends, which lies transversely in the ventral wall of the abdomen. To each end is attached a long _basal_ cartilage which lies in the fin, close to and parallel with its inner margin. A proximal series of slender _radial_ cartilages is attached to the lateral side of the basal; a distal series of very short radials lies outside of the first series, while the portion of the fin beyond these is supported by the dermal fin-rays.