A treatise on zoology . F. Koemer (1860, W. & Sp.,1897) ; IBB large, anchylosed ; anal tube cen-tral ; arms supposed to be 5 rami bearing alter-nate ramules, but are not known beyond IIIBr^(Fig. CXXIV.). Si2)honocrinus, S. A. Miller(1888, em. W. & Sp., 1897) ; IBB small; rectumforms an asymmetric protuberance below, thencurves subtegminally either to a central analtube, or right across to an anterior opening ator even beneath the arm-bases. Family 4. Ehodocrixidae. Dicyclica Cam- , . . . ^^ T • Lampterocrimis tennesseensis, erata with RR separated by a single distinct from posterior interradiu
A treatise on zoology . F. Koemer (1860, W. & Sp.,1897) ; IBB large, anchylosed ; anal tube cen-tral ; arms supposed to be 5 rami bearing alter-nate ramules, but are not known beyond IIIBr^(Fig. CXXIV.). Si2)honocrinus, S. A. Miller(1888, em. W. & Sp., 1897) ; IBB small; rectumforms an asymmetric protuberance below, thencurves subtegminally either to a central analtube, or right across to an anterior opening ator even beneath the arm-bases. Family 4. Ehodocrixidae. Dicyclica Cam- , . . . ^^ T • Lampterocrimis tennesseensis, erata with RR separated by a single distinct from posterior interradius. IB,plate in each IR, followed by well-defined iBr StoSs?,!?<; oVyx.(Aft?rregularly arranged (some individuals of Lyrio- c. F. Roemer.) x |.crinus have RR not quite separated, and some species of Diaholocrinus have not the single distinct interradial) ;the anal area is not always distinct, and but rarely has a vertical series ofplates. IBr, 2, in all except the rather doubtful Anthemocrimis. Arms free. Fig. CXXIV. 200 THE CRINOIDEA above IIBr (except in Thylacocrinus) ; illBr may or may not be plates of the tegmen are small and usually irregular. The familybegins in the Ordovician, probably as an independent development fromReteocrinidae or similar forms, and runs parallel to the Dimerocrinidaethrough the Silurian, but, unlike them, persists to Carboniferous is seen in it an increase in definiteness of iBr, and the origin ofbiserial arms, which are usually isotomous but exceptionally bear —Rhaphanocrinus, Vi. & Sp. (1885 ; syn. Coelocrinus, Salter),Ordovician, N. America, Gt. Britain, has uniserial arms and numerous iBrand illBr. Archaeocrmus, W. & Sp.(1881), Ordovician, N. America, hasBr in zigzag, numerous iBr moreregular in arrangement, with no verti-cal series in anal IR (Fig. CXXV.).Diaholocrinus, W. & Sp. (1897), Ordo-vician, N. America, has the largerand more regular iBr surrounded bysupplementary plates ; the anus isat the
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