CLASS I 



CYSTOIDEA 



157 



Order 4. APORITA Zittel (emend.). 



Radial symmetry affects food-grooves and calyx plates. Food-grooves home on 

 processes around the oral centre. No folds, rhombs or diplopores. 



This division is admittedly artificial and ill-defined, being chiefly a 

 receptacle for genera whose relations are imperfectly understood, or whose 

 systematic position is doubtful. 



Family 1. Cryptocrinidae Zittel. 



Calyx composed of three rings of very finely perforate or imperforate, someivhat 

 regularly arranged plates. Mouth central, snrroimded by articidar facets for the 

 attachment of small arms. Anus eccentric; stem round and 

 slender. Ordovician to (?) Permian. 



Cryptocrinus v. Buch (Fig. 248). Base composed of 

 three plates, and surmounted by two zones, each con- 

 taining five plates of unequal sizes. Mouth and anus 

 enclosed within a ring of smaller pieces. Ordovician ; 

 St. Petersburg. C. cerasus v. Buch. 



Lysocystites Miller {Echinocystites Hall non Wyv. 

 Thomson, Scolocystis Gregory). Silurian (Niagara 

 Group) ; North America. 



Hypocrinus Beyrich. This 

 genus, described as a Cystid, 

 from the Permian in the island 

 of Timor, and Coenocystis Girty, 

 from the same formation in 

 western America, are probably 

 Crinoids. 



Fig. 249. 



Macrocystella marlae Call. 

 A, from side X 1/1 . B-D, por- 

 tion of a brachiole, XiS/1, 

 from side, dorsal and ven- 

 tral surfaces. B, single plate 

 enlarged (after Bather). 



Fig. 248. 



Family 2. Macrocystellidae 

 Bather. 



Calyx consisting of three or four 



circlets of plates, displaying more Cryptocrinus cemsnsv Buch. 



■' -^ .' -^ "^ "^ Ordovician ; Pulkowa, Russia. 



or less pentamerism. JSO pores or a, l, c, Calyx from one side, 



,7 ry \ • from abo\'e, and from below 



rhombs. Oam brian. („at. size); m, Mouth ; «, Anus. 



Macrocystella Calloway. 

 (Mimocystites Barr.) (Fig. 249). Three ranges of five plates each, followed 

 by a fourth of the same number bearing bifurcating brachioles. Radiating 

 folds strongly marked, dividing surface into triangles. No rhomb structure 

 visible. Stem rapidly tapering. Pentamerous symmetry is well marked, 

 and the form might be characterised as a tri-cyclic Crinoid. Cambrian ; 

 England. 



Lichenoides Barr. (Lichenocystis Haeckel). Cambrian ; Bohemia and 

 Bavaria. Aethocystis S. A. Miller. Silurian ; Indiana. 



Family 3. Tiaracrinidae Bather (emend.). 



Calyx composed of not more than two circlets of plates : three (basals) in the first, 

 and four (radials) in the second ; followed by a range of short plates resembling 



