CLASS I 



CYSTOIDEA 



151 



the convcx side. Arms feeble, filiform. Ordovician and Silurian ; North 

 America, England, Bohemia. 



Balanocystites Barr. Ordovician ; Bohemia. 



Belemnocystis Miller and Gurley. Ordovician ; North America. 



Placocystites de Koninck (Fig. 236). Silurian ; England. 



Dendrocystites Barrande. Ordovician ; Bohemia. Cigara Barrande. Cam- 

 brian ; Bohemia. Syringocrinus Billings. Trenton Group ; Canada. 



Eocystites Billings. Cambrian ; Canada. 



Protocystis Hicks. Cambrian ; England. 



Ceratocystis Jaekel. Cambrian ; Bohemia. 



Fig. 236. 



Placocystites forhcsianus de Kon. Silurian ; Dudley, 

 England. A, Concave aspect, showing brachioles (br) 

 and proximal stem joints. B, Convex aspect. b, basals ; 

 m, niarginals ; v, ventrals (after Jaekel). 



Fig. 237. 



Amygckducystites florealis Bill. Tren- 

 ton Group ; Canada. 1, from side ; 2, 

 Single plate enlai-ged ; 3, portion of 

 food-groove enlarged. Br, dotted 

 outline of sonie brachioles ; Br', facet 

 for attachment of same (after Bather). 



Family 3. Malocystidae Bather. 



Calyx plates numerous and indefinitely arranged. Radial folds of stereom 

 strongly marked, hut no definite pore-rhombs or peäinated rhomhs. Brachioles borne 

 on processes either free or recumbent on the calyx. Stem uniserial. 



Malocystis Billings. Calyx globular. Ordovician ; Canada. Canadocystis 

 Jaekel. Sanre horizon. 



Sigmacysiis Hudson. Ambulacra S-shaped. Ordovician ; Canada. 



Amygdalocystites Billings (Fig. 237). Calyx flattened and elongate. Two 

 unbranched ambulacra, fringed with brachioles, pass from a subcentral mouth 

 over the calyx. Ordovician ; Canada. 



Comarocystites Billings. Ordovician ; Canada. Achradocystites Volborth. 

 Ordovician ; Russia. 



Order 2. RHOMBIFERA Zittel (emend. Bather). 



Radial symnietry affects food-grooves, and sometimes calyx plates. Food-grooves 

 borne on jointed processes (brachioles). Calyx plates more or less folded, and provided 

 with rhombs. 



