154 



ECHINODERMATA— PELMATOZOA 



PHYLUM IV 



the base flat or truncated ; plates twenty-five iii number. Arms sometimes 

 bifurcating. Silurian ; North America. 



Apiocystites Forbes. Calyx regularly oval, elongate or slightly compressed, 

 and composed of nineteen plates. Silurian ; England, Sweden and North 

 America. 



HaUicystis Jaekel. Like the preceding, except in having five deltoid 

 plates instead of one. Silurian. 



Lepocrinites Conrad (Lepocrinus or Lepadocrimis Hall ; Staurocystis Haeckel). 

 Silurian ; New York and Tennessee. 



Lepadocystis Carp. {Meekocystis Jaekel). Ordovician ; North America. 



Sphaerocystites Hall ; Coelocystis, Jaekelocystis, Tetracystis and Trimerocystis 

 Schuchert. Silurian ; North America. 



Strobilocystiies White. Devonian ; North America. Hyhocystiies Wetherby 

 Silurian ; North America. 



A B 



Fig. 242. 



Callocystites jeiiHti Hall. Sil- 

 urian (Niagara Grouj)) ; Lock- 

 port, New York. Calyx seen 

 from one side (natural size), a, 

 anus ; hr, braclnoles, p, pectino- 

 rhombs. x J (after Jaekel). 



Pig. 243. 



I'leurocystUesJUitextiis Billings. Ordovician ; OttaAva, 

 Canada. A, Calyx from the anterior side. /!, Same 

 from the anal side ; A, anal area ; a, anus ; h, basals ; 

 br, braclnoles ; g, genital aperture ; I ^-'^, laterals ; m, 

 madrei)orite. x J (after Jaekel). 



Subfamily B. Glyptocystinae Jaekel. 



Pleurocystites Billings (Fig. 243), Convex side with large plates arranged 

 in cycles ; flattened side covered with very minute plates. Three isolated 

 pore-rhombs borne on the convex side. Arms two in number, robust. Stem 

 round, tapering distally to a point. Ordovician ; Canada. 



Glyptocystites Billings. Ordovician ; Canada and Russia. 



Cheirocrmus Eichwald ; Cystohlastus Volborth. Ordovician ; Russia. 



Homocysiites Barrande. Ordovician and Silurian ; Bohemia. 



Subfamily G. Echinoencrininae Jaekel. 



Echinoencrinus v. Meyer (Sycocysfites v. Buch and Gonocrinites Eichw.) (Fig. 

 244, A). Calyx composed of four basal plates, and three cycles containing five 

 plates each. All calycine plates ornamented with costae or ridges radiating 



