CLÄSS I 



CYSTOIDEA 



155 



B 



outward from the ceiitre. Ventral surface with short ambulacral grooves, and 

 articular facets for the attachment of three small arms. Anus removed to a 

 iateral position between the first and 

 lecond circlet of side plates. Three 

 ^pore-rhombs present ; of these, two are 

 situated above the base on the side 

 opposite the anus, and the third above 

 and slightly to the right of the anus. 

 Stem round, short, tapering distally 

 to a point, and composed of hollow 

 Segments inserted one within the other 

 like the draw - tubes of a spy-glass. 

 Ordovician; Kussia. * 



ScoUocystis, Erinocystis (Fig. 244, B) 

 and Glaphjrocystis Jaekel. Ordovician ; 

 Russia. 



Prunocystis Forbes. 



Schizocystis Jaekel. Silurian ; England 



Fig. 244. 



A, Echinoencrinus senckenbergi v. Meyer. B, 

 Erinocystis volhorthi Jaekel. a, anus ; h, basals ; l, 

 laterals ; p, pectino-rhombs. x | (after Jaekel). 



Order 3. DIPLOPORITA Zittel (emend. Bather). 



Radial symmetry affects food-grooves, and to some extent the calyx plates connected 

 therewith. Food-grooves extended over the ccdyx plates themselves, and prolonged to 

 brachioles which line the calyx grooves. Pectinated rhombs and pore-rhomhs not 

 developed ; hut calyx plates may he folded, and diplopores always present. 



Family 1. Sphaeronitidae Neumayr. 



Calyx globular or cylindrical, short-stemmed er stemless, and composed of 

 numerous irregularly arranged plates with pores united in pairs. Ambulacral 



grooves either open or protected by 

 A ß covering plates, and either short and 



simple, or elongated and branching, 

 not extending from the mouth beyond 

 the adoral circlet of plates. Arms 

 ür«><Ss/2^Tft»r'^ . ö^s a rule exceedingly small and 

 primitive. Ordovician and Sil- 

 urian. 



Sphaeronites Hising. {Pomo- 

 cystis Haeckel) (Fig. 245). Glo- 

 bose, stemless. Five short ambu- 

 lacral grooves radiating from the 

 mouth towards the arm bases. 

 Ordovician (Vaginatenkalk) ; 

 Russia, Sweden and England. 

 S. pomum Gyll. 



Eucystis Angelin. Ordovician ; Sweden. 



Trematocystis, Palmocystis, Archegocystis and Codiacystis Jaekel. Ordovician ; 

 Bohemia. 



Allocystites S. A. Miller. Silurian ; North America. 



Fig. 245. 



Sjihacronites globulus Angelin. Ordovician, Sweden. A, 



Theca, lateral aspect. B, Oral aspect, enlarged. an, anus ; 



hr, facets for attachment of brachioles ; g, genital aperture ; 



0, mouth ; x, base for flxation. 



