CLASS I 



CYSTOIDEA 



153 



facets for the attachment of arms. Pore-rhombs present on all of the side 

 plates. Ordovician ; Russia. H. pyriformis v. Buch. 



Caryocrinus Say {Stribalocystis S. A. Miller ; Enneacystis Haeckel) (Fig. 

 240). Calyx hexamerous, with dicyclic base. Infrabasals four, unequal; 

 followed by a second row (basals) 

 of six jDlates, alternating with the 

 plates of the first and third cycles. 

 The latter ring consists of eight 

 plates, six of which, according to 

 Carpenter, represent the radial s, 

 and two (the interscapulars of 

 Hall) the interradials. Ventral 

 surface formed of six or more 

 small pieces. All plates of the 

 cup furnished with pore-rhombs ; 

 the summit plates imperforate. 

 Mouth and ambulacral groove 

 subtegminal. Anus protected 

 by valvular pyramid, and situated 

 on the outer margin of the ventral 

 surface. Here also ai'e placed 

 the arms, which are six to thirteen 



in number, and relatively feeble. Stem long, composed of cylindrical 

 segments. Ordovician ; Scandinavia. Silurian ; New York and Tennessee. 



Heterocystites Hall. Silurian ; New York. Corylocrinus, Juglandbcrinus 

 von Koenen. Upper Ordovician ; France. 



Fig. 240. 



C'aryocrinus ornatus Say. Silurian ; Lockport, New York. 

 II, Calyx from one side, with two arms attaclied ; ft, Summit, 

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

 second circlet, with pore-rhombs. 



Family 3. Oallocystidae Bernard. 



Calyx composed of large plates arranged in three to five cycles, and exhibiting 

 three to fim pectinated rhombs, the component halves of which stand on contiguous plates, 

 and are separated by an interval. Mouth forming the centre of radi- 

 ation for two to five brachioliferous food-grooves which are protected 

 by covering pieces, and either rejwse upon the calyx, or are sunk below 

 the surface in grooves. Stem well developed, tapering distally to a 

 point. Ordovician and Silurian. 



Subfamily A. Callocystinae Jaekel. 



Pseudocrinites Pearce (Fig. 241). Calyx ovate, 

 two- to four-sided, and composed of four cycles 

 of polygonal plates. Anus closed by valvular 

 pyramid, and occupying a lateral position. Pore- 

 rhombs three in number; one placed above the 

 base, the remaining two to the right and left of 

 the anus. Arms two to four, recumbent upon the 

 calyx, extending to the base, and beset with biserial 

 jointed pinules. Stem robust. Silurian ; England. 



Callocystites Hall {Anthocystis Haeckel) (Fig. 242). 

 Calyx olive-shaped, the oral end being more attenuated and obtusely pointed, 



Fig. 241. 



Pseiodocrinites quadnfaseiatus 

 Pearce. Silurian ; Tividale, Eng- 

 land. A, Calyx from one side. 

 B, Summit, sliowing mouth (»i), 

 anus (o), and tliree "of the arms. 

 The fourth arm (.);), broken away, 

 exposing flattened surl'ace of calyx. 



