CLASS I 



CYSTOIDEA 



155 



B 



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



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



lateral position between the first and 



second 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. 



Scoliocystis, Erinocystis (Fig. 244, B) 

 and Glaphyrocystis Jaekel. Ordovician ; 

 Russia. 



Prunocystis Forbes. 



Schizocystis Jaekel. Silurian ; England. 



Pig. 244. 



A, Echinoencrinus senckenhergi v. Meyer. B, 

 Erinocystis volhorthi Jaekel. a, anus ; '), basals ; I, 

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



Order 3. DIPLOPORITA Zittel (emend. Bather). 



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

 thereivith. Food-grooves extended over the calyx plates themselves, and prolonged to 

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

 developed ; but calyx plates may be folded, and diplopores always present. 



B 



Family 1. Sphaeronitidae Neumayr. 



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

 numerous irregularly arranged plates with pores united in pairs. Ambulacral 



grooves either open or protected by 

 covering plates, and either short and 

 simple, or elongated and branching, 

 not extending from the mouth beyond 

 the adoral circlet of plates. Arms 

 as a rule exceedingly small and 

 primitive. Ordovician and Sil- 

 urian. 



Sphaeronites Rising. (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. 



Pig. 245. 



Sphaeronites globulus Angelin. Ordovician, Sweden. A, 

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

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

 0, mouth ; x, base for fixation. 



