CLASS II 



CYSTOIDEA 



185 



If.micosmites, v. Buch. Calyx composed of four basal plates two zones 

 ,ontainin- six and nine lateral plates respectively, and a circlet of six plates 

 forming the rented rarfcee. The latter carries three short ambulacral 

 grooves, at the ends of which are situated small articular facets for the 

 attachment of arms. Rhomb-pores present on all of the side plates. 

 vi.-ian : Russia. H. //////'///*, v. Buch. 



Btt^m'/ms- Say (Fi- 305). Calyx hexameroui, with dicyclic base. 

 Infrabasals four, un.- M ual; followed by a second row (basals) of i ;es, 



alternating with 

 the plates of the 

 first and third 

 cycles. The latter 

 ring consists of 

 eight plates, six 



of which, arc.. fd ^BBsrsv i^me^m >> 



ing to Carpenter, 

 represent the 

 radials, and two 

 (the interscapu- 

 lars of Hall) the 

 interradials. Ven- 

 tral surface 

 formed of six or 

 more small pieces. 

 All plates of the 

 cup furnished 



with pore-rhombs ; the summit plates imperf orate. Mouth and ambulacral 

 grooves subtegminal. Anus protected by valvular pyramid, and situated on 

 the outer margin of the ventral surface. Here also are placed the arms, which 

 are six to thirteen in number, and relatively feeble. Stem long, composed of 

 cylindrical segments. Silurian ; North America (New York and Tennessee). 



Echinoencrinus, v. Meyer (Sycocystites, v. Buch), (Fig. 306). Calyx com- 

 posed of four basal plates, and three cycles containing five plates each. All 

 calycine plates ornamented with costae or ridges radiating 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 draws of a spy-glass. Ordovician ; Russia. 



Glyptocystites, Billings. Ordovician ; Canada and Russia. 



Homocystites, Mimocystites, Barrande. Ordovician ; Bohemia. 



Family 7. Anomalocystidae. Woodward. 



Calyx more or less compressed, frequently with dissimilarly plated anterior and 

 posterior sides. Plates either imperf orate or with simple pores ; pore-rhombs absent or 

 but few in number. Arms free ; stem short, tapering distally to a point. Cambrian 

 to Silurian. 



FIG. 305, 

 ornatus, Say. Silurian ; Lockport, New York. 



, CaTyx from one side, with two arms attached ; b, Summit, 

 natural size ; c, Inner and outer surfaces of calyx plate of the 

 second circlet, with pore-rhombs. 



FIG. 



Echinoencrinus 

 striatus, v. Buch. 

 Ordovician ; St. 

 Petersburg, i 



