. The Danish Ingolf-Expedition. Scientific expeditions; Arctic Ocean. ON THE APPENDICES GENITALES iCEASPERS) IN THE SELACHIANS. r9 dorsal one (Rd), and the ventral one (Rv); posteriorly they always reach to the end-style, anteriorly more or less forward, commonly not to the same length, and at most to the proximal end of the appendix-stem. Together with this they form the chief piece* of the appendix-skeleton, a name used by several earlier authors, who most frequently have not seen that this piece consists of three parts. The other secondary cartilages, the terminal pieces, together with the
. The Danish Ingolf-Expedition. Scientific expeditions; Arctic Ocean. ON THE APPENDICES GENITALES iCEASPERS) IN THE SELACHIANS. r9 dorsal one (Rd), and the ventral one (Rv); posteriorly they always reach to the end-style, anteriorly more or less forward, commonly not to the same length, and at most to the proximal end of the appendix-stem. Together with this they form the chief piece* of the appendix-skeleton, a name used by several earlier authors, who most frequently have not seen that this piece consists of three parts. The other secondary cartilages, the terminal pieces, together with the end-style form the skeleton of the terminal part, and are more or less movably connected mutually, with the marginal cartilages, and with the end-style. The number of terminal pieces may be different, but in all Plagi- ostomes two are found, one dorsal (Td), and one ventral (Tv), placed as a kind of movable continua- tion of the two marginal cartilages, and with their inner edges joining the end-style of the axial piece, which bv being bent (ventro-medially) is moved in connection with them; thereby they dorsally withdraw more from each other, and the slit between them is widened. Only in a few cases (Trygon violacea, Chlamydoselackus) these two pieces are found alone; in most Sharks a piece Td2 is joined to the lateral margin of Td, and imbedded together with this in the dorsal lip of the appendix-slit; often a piece Tv2 is in a like manner joined to Tv\ further is gene- rally found a piece T3, placed veutrally and laterally, and often rising through the skin as a spur or thorn; still more pieces may be developed (especially in Raja), but their homologies in the different forms are gener- ally easily pointed out, and are in the special part indi- cated by the letters used. Finally may to the terminal pieces proper be joined one or more «spurious- pieces or covering pieces, enclosing like a shield the terminal pieces, properly so called, on the dorsal side (d) or the ventral s
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectscientificexpedition
