. The Bashford Dean memorial volume :. Fishes; Sharks; Fishes, Fossil. Text-figure 41. Pectoral fins of the fossil sharks (A) Cladoselache, (B) Ctenacanthus, and (C) Cladodus neilsoni, indicating the mode of origin of the metapterygial axis. B, basalia; M, muscle of hindmost region of the fin; R, radials; SC, shoulder girdle. After Dean, 1909, Fig. 28. homologi7;ed with a basal in recent fishes, and it is considered to be a metapterygium. In front of this element there is, apparently, a series of radials in direct articulation with the pectoral girdle. In Symmorium the metapterygium itself sho
. The Bashford Dean memorial volume :. Fishes; Sharks; Fishes, Fossil. Text-figure 41. Pectoral fins of the fossil sharks (A) Cladoselache, (B) Ctenacanthus, and (C) Cladodus neilsoni, indicating the mode of origin of the metapterygial axis. B, basalia; M, muscle of hindmost region of the fin; R, radials; SC, shoulder girdle. After Dean, 1909, Fig. 28. homologi7;ed with a basal in recent fishes, and it is considered to be a metapterygium. In front of this element there is, apparently, a series of radials in direct articulation with the pectoral girdle. In Symmorium the metapterygium itself shows a segmentation, probably metameric, along its distal margin. If the above interpretations are correct, they afford evidence that basals are developed by the concrescence of proximal segments of radials. For comparison I have inserted Dean's (1909) figures (my Text-figure 41) of the pectoral fins of Cladoselache, Ctenacanthus and Cladodus neilsoni. The origin of the girdles (discussed on p. 376) is obscure, but there seem to be sufficient data to warrant an acceptance of the theory of the metameric origin of the basals of the paired fins. PELVIC FINS AND PELVIS Since the pelvic fins of the male Chlamydoselachus are highly modified to form copu' latory organs (myxopterygia), it is necessary to describe the pelvic fins of the two sexes separately. Pelvic Fins and Pelvis of the Female.—The pelvis and the pelvic fin skeleton of the female Chlamydoselachus have been described and figured by Garman (), Deinega (1909 and 1923), and Goodey (). The figures by Garman and by Goodey are reproduced as my Text-figures 42, 43, and 89 (p. 434). The pelvis of Chlamydoselachus, as compared with that of Heptajichus, is very long (, in the direction of the principal axis of the body). Commenting on this fact, Garman Text-figure 42. Dorsal view of the pelvis (one-half natural size) of an adult female Chlamydoselachus. hp, basipterygium; il, iliac ridge; pu, pubis. Redrawn after
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