CLASR TU 



CRINOIDEA 



199 



§ 1. Rays with two or more primilrrachs (costals). 



Coccocrinus Job. Müller. The simplest form of the Camerata, the calyx 

 consisting only of three basals, five radials, 2x5 costals, five interbrachials and 

 five orals. Calyx small, rotund ; basals and radials forming almost the entire 

 dorsal cup. Tegmen almost completely occupied by five large, triangulär, 

 symmetrical orals, forming a pyramid. Anal opening in the interradio- 

 oral suture. Arms delicate, branching once, uniserial with cuneate joints. 

 Column round. Silurian ; North America. Devonian ; Eifel. 



Culicocrinus Joh. Müller. Transitional between Coccocrinus and Platycrinus ; 

 generally similar to the former. Orals asymmetrical. Arms heavy, biserial. 

 Column round. Middle Devonian ; Eifel. 



Hapalocrinus Jaekel em. Bather {Agriocrinus, Thallocrinus and Clematocrinus 

 Jaekel). Orals small ; interambulacra visible. Arms uniserial, with cuneate 

 joints ; branching once or twice. Column round, with strong cirri. Silurian ; 

 England, Australia, North America. Devonian ; Germany. 



Cordylocrinus Angelin. Tegmen composed of numerous plates. Arms 

 uniserial, or slightly interlocking. Column round, with long cirri. Silurian ; 

 Gotland. Devonian ; North America. 



§ 2, Eays with only one primibrach (costal). Orals occupying but a small part of 

 the tegmen, asymmetrical ; ambulacral plates well defined. 



Marsipocrinus Bather {pro Marsupiocrinus Phill., nm Blv.). (Syn. Cypellocrinus 

 vel Cupellaecrinus Shumard, ex Troost, non Steininger.) Brachials to axillary 

 distichal usually incorporated in cup. Arms biserial, ten or twenty. Column 

 round. Axial canal large. Silurian ; England, Gotland, North America. 



Fig. 300. 

 Platycrinus suhspinomn (Hall). Lower Carbonifer- 

 ous; Burlington Group, Iowa. Analysis of dorsal 

 cup, omitting anal Interray. h, Basals ; R, radials ; 

 I, Costals; ir, Interbrachials (after Wachsmuth 

 and Springer). 



Fio. 301. 

 Platycri iius triginti(lactyliu<< 

 (Austin). Lower Carbonifer- 

 ous ; Tournay, Belgiuni (re- 

 stored, after de Koninck). 



Platycrinus Miller {Centrocrinus, Pleurocrinus Austin; Edwardsocrinus d'Orb.) 

 (Figs. 300, 301). Calyx rotund. Radials large with crescent-shaped facets. 

 First interbrachials at the level of the arm bases ; consisting of three plates 

 horizontally arranged, usually partly interambulacral, but sometimes succeeded 

 by one or more ranges incorporating the distichals ; plates of anal interradius 

 usually more numerous than those of the other sides. Orals usually large, 

 asymmetrical, occupying but a small part of the tegmen. Ambulacra rigid, 



