< KINOIDEA CAMKRATA 145 



Xe*ocrm**i S. A. Miller. IB obsolete; B four; (-(,11111111 M uadran,'ular. 

 < Hli<T\\ isc ivst-mbling /,V/"/ov'////s. ( )rdovician ; North America. 



Family 0. Thysanocrinidae. AYarli-mutli and Springer. 



(d/it/.fni-riii'nlai; pp. Zittel ; (///////.</> /-/W,, s Angelin.) 



AW- ,//>//,-//>. 7,'<"//Vx /,/A-/W/// /// confo4 casegrf "/ ///'- interior side, where they 

 are sepr<i1<'<l lij mi a, ml ji/afr. Thi* in follmwd !>// wwrnl rows o/ interradials, 

 between which additional tum/.< or inf, rj>oed. Ordovician and Silurian. 



[Thysanocrinidae was substituted by W. and Sp. as a family name, on dis- 

 covering the identity between </////</</./</, /iiutrrm-riiius, Eucrinus, and Thysano- 

 crinus. The last-named genus is entitled to priority, from being the first to 

 have received a tolerably accurate description. Glyptocrinus, Hall, and Stelidio- 

 cr'mus, Ang., are removed to the MelocrinidaeJ] 



ThiiHuun'iiiitix, Hall (Glyptaster, Hall; Dimerocrinus, Phill. ; Eucrinus, Ang.) 

 Calyx deep. IRA followed by three plates. Arms ten to twenty, biserial. 

 Silurian (Niagara Group) ; North America, England, Gottland. 



JIf//)tiocrinus t W. and Sp. Dorsal cup saucer-shaped, almost flat ; the larger 

 plates of the tegmen spiniferous. Arms pendent. Niagara Group ; North 

 America. 



Ptyclwcrinus, W. and Sp. Like Thysanocrinits, but arms uniserial. Ordovician ; 

 North America. 



Idiocrinus, W. and Sp. IR represented by a single large interbrachial in 

 each of the interrays ; that of the posterior side resting upon IRA. Niagara 

 Group ; North America. 



Spyridiocrinus, Oehlert. Devonian ; Saint Malo, France. 



Lampterocrinus, Roem. Like Thysanocrinus, but having an anal tube ; IE A 

 large, and succeeded by three longitudinal rows of IR. Silurian (Niagara 

 Group) ; North America. 



Orthocrinus, Jaekcl. Devonian ; Rhineland. 



Family 7. Rhodocrinidae. Eoemer. 



Base dicyclic. Infnibasals five ; lasals five, pentagonal, truncated at the upper end. 

 The radials separated all around by large interradials. Anal area but very slightly, 

 often not at all different from those of the other interrays. The rays generally free 

 above the disticlials ; primari/ urutx rarely more than ten, and either simple or branching. 

 Pinnules long and closely abutting. Ordovician to Sub-Carboniferous. 



Rhodocrinus, Miller (Acanthocrinus, Roem.) Calyx small, composed of delicate 

 plates. IB frequently hidden by the column. B and IR large ; the latter 

 rapidly decreasing in size upward. Rays free from the distichals upward, and 

 the ten primary arms branching once or oftener in the free state. Arms biserial, 

 thin, and moderately short; pinnules closely crowded, long, and slender. Column 

 round ; axial canal stelliform. Ordovician to Middle Sub-Carboniferous ; Europe 

 and North America. 



Archaeocrinus, W. and Sp. Calyx obovate. IR numerous, and enclosing 

 a supplementary anal in the second or third row. Interdistichals generally 

 present. Arms uniserial, branching. Ordovician ; Canada. 



RhaphanocrinuSy W. and Sp. Like the preceding, but with large IB, 

 which are exposed in a side view. Arms long, simple, and uniserial. Ordo- 

 vician ; Ohio and Indiana. 



VOL. I L 



