A treatise on zoology . Fk;. Caudal vertebrae of Thynnus vidparis (Cuv. and Val.)- A, right-side view ; B, left-sideview of the same cut in half, , anterior ventral jirocess ; «.;, anterior zjjgapopliysis : ; , haemal arch; , neural arch; , posterior ventral process ; i).2, posterior zygapophysis; r place of attachment of rib. BONE 355 structure (Figs. 340, 341). This is brought about l)y the reductionof the extreme tip of the heterocercal or homocercal fin in the laterstages of development; such a false or secondary diphycercal fin iscalled gephyrocercal (Kyder [3
A treatise on zoology . Fk;. Caudal vertebrae of Thynnus vidparis (Cuv. and Val.)- A, right-side view ; B, left-sideview of the same cut in half, , anterior ventral jirocess ; «.;, anterior zjjgapopliysis : ; , haemal arch; , neural arch; , posterior ventral process ; i).2, posterior zygapophysis; r place of attachment of rib. BONE 355 structure (Figs. 340, 341). This is brought about l)y the reductionof the extreme tip of the heterocercal or homocercal fin in the laterstages of development; such a false or secondary diphycercal fin iscalled gephyrocercal (Kyder [378]). The structure of the actualupturned tip of the notochord varies greatly, being naked in EiiOi\with a cartilaginous sheath in Salmo, Elops, etc., a bony urostyle in. Skeleton ol the extremity of the tail of Fierasfer dentatus, Cuv. (After Emery.)?, lepiilotricli ; v, last vertebra. Acanthopterygii and others. Special bony plates may lie on eachside of it (Fig. 63) (Lotz [286]). It is to be noticed that although the caudal fin is chiefly ofhypochordal origin (p. 104), }et a considerable portion of the upperlobe may ])e derived from the epichordal fin (Fig. 46). Thecomposition of the caudal fin thus varies in different families, anda more exact study of its development might yield useful results.
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Keywords: ., bookcentury1900, bookdecade1900, bookpublishe, booksubjectzoology
