. The Cambridge natural history. Zoology. PECTORAL AND PELVIC GIRDLES 239 fins, in some of the Lower Devonian Acanthodei ( Climatius), may be regarded in that light. The Pectoral and Pelvic Girdles.âThe 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 distinct- ness. Existing Elasmobranchs, in- cluding the Holo- cephali, have
. The Cambridge natural history. Zoology. PECTORAL AND PELVIC GIRDLES 239 fins, in some of the Lower Devonian Acanthodei ( Climatius), may be regarded in that light. The Pectoral and Pelvic Girdles.âThe 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 distinct- ness. Existing Elasmobranchs, in- cluding the Holo- cephali, 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 ventral is the cora- coid. Between these two portions of the girdle, and defining their limits, there are articular surfaces for the basal cartilages of the pectoral fin. 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. the ^I"- 1^1-â'^^'^ 'â 'g''* '^^^^ °^ ^'^ pectoral girdle and the fin of an Elasmobranch (ChilosajUium). Dermal horny fibres ; meso, niesopterygium ; meta, metapteryginni ; pect, pectoral girdle ; pro, propteryginm. (From Parker and Haswell.). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Harmer, S. F. (S
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
