OCR Text |
Show 1881.] OF THE PAIRED FINS OF ELASMOBRANCHS. 663 a small zone at the base of the fin, the remainder being formed of a fringe supported by radiately arranged horny fibres1. The true skeleton consists of three basal pieces articulating with the pectoral girdle ; on the outer side of which there is a series of more Pectoral fins and girdle of an adult of Scyllium canieula (natural size, seen from behind and above.) co. Coracoid; sc. scapula; pp. propterygium ; mep. mesopterygium; mp. metapterygium ; fn. part of fin supported by horny fibre. Fig. 2. Right pelvic fin and part of pelvic girdle of an adult female of Scyllium canieula (natural size). il. iliac process; pn. pubic process, cut across below ; bp. basipterygimn; af. anterior cartilaginous fin-ray articulated to pelvic girdle; fn. part of fin supported by horny fibres. or less segmented cartilaginous fin-rays. Of the basal cartilages one (pp) is anterior, a second (mep) is placed in the middle, and a third is posterior {mp). They have been named by Gegenbaur the pro- 1 The horny fibres are mesoblastic products; they are formed, in the first instance, as extremely delicate fibrils on the inner side of the membrane separating the epiblast from the mesoblast. |