_The Pectoral and Pelvic Girdles_.—The pectoral girdle is more primitive in _Cladoselache_ and _Pleuracanthus_ than in any other Elasmobranch. In the former (Fig. 145, A) it may be doubted if the girdle has passed beyond the basipterygial stage, and although a definite girdle is present in the latter genus (Fig. 250) its lateral halves retain their primitive distinctness. Existing Elasmobranchs, including the Holocephali, have a pectoral girdle in the form of a dorsally incomplete hoop of cartilage imbedded in the muscles of the body-wall, close behind the last branchial arch (Fig. 141). The upper or dorsal portion of each half is the scapula, and the ventral is the coracoid. Between these two portions of the girdle, and defining their limits, there are articular surfaces for the basal cartilages of the pectoral fin. [Illustration: FIG. 141.—The right half of the pectoral girdle and the fin of an Elasmobranch (_Chiloscyllium_). _d.r_, Dermal horny fibres; _meso_, mesopterygium; _meta_, metapterygium; _pect_, pectoral girdle; _pro_, propterygium. (From Parker and Haswell.)] _Cladoselache_ (Fig. 145, B) had no pelvic girdle, nor does it appear that this primitive Elasmobranch had acquired even a basipterygium. _Pleuracanthus_, on the contrary, had a pair of pelvic rudiments distinct from well-developed basipterygia. In other Elasmobranchs there is a distinct girdle, formed by the median union of primitively distinct lateral rudiments, consisting of a simple transverse bar of cartilage, imbedded in the ventral abdominal wall, just in front of the cloacal aperture, and having articulated to each of its outer extremities the basal cartilage (metapterygium) of the pelvic fin. {240}[Illustration: FIG. 142.—The left half of the pelvic girdle and the right pelvic fin of _Chiloscyllum_. _meta_, Metapterygium; _pelv_, pelvic girdle. (From Parker and Haswell.)] [Illustration: FIG. 143.—Left half of the pectoral girdle of a Trout (_Salmo fario_), seen from the inner surface. _CL_, Clavicle (cleithrum); COR, coracoid; _D.F.R_, dermal fin-rays; MS.COR, meso-coracoid; _P.CL_, _P.CL′_, post-clavicles; PTG.1, proximal; _ptg.2_, distal pterygiophores; _P.TM_, post-temporal; _S.CL_, supra-clavicle; SCP, scapula. (From Parker and Haswell.)]