186 ECHINODERMATA—PELMATOZOA SUB-KINGDOM III 
Trochocystites, Barr. Calyx strongly compressed. Plates of the rightand 
left sides large, those of both the anterior and posterior small, polygonal. 
All plates perforate, but without pore-rhombs. Ventral surface with three 
apertures. Stem com- 
posed of several vertical 
rows of plates. Cam- 
brian ; Bohemia, Spain, 
Northern France. 
Mitrocystites, Barr. 
Like the preceding, ex- 
cept that one side of the 
calyx is composed of toler- 
ably large, and the other 
of small plates. Ordo- 
vician ; Bohemia. 
Anomalocystites, Hall 
(Aeteleocystites, Bill.) 
Calycine plates smaller 
ee aes and more numerous on 
Pleurocystites squamosus, Billings. Ordovician; Ottawa, Canada. the convex side than 
a, Calyx from the anterior side; b, Same from the anal side; c, Arms, 9n the concave. Anus 
enlarged. Right and left reversed (after Billings). : 
situated very low down 
on the convex side. Arms feeble, filiform. Ordovician and Silurian; North 
America, England, Bohemia. 
Balanocystites, Dendrocystites, Barr. Ordovician ; Bohemia. 
Pleurocystites, Bill (Fig. 307). 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. 


Fia. 308. 
Pseudocrinites quadrifasciatus, 
Pearce. Silurian; Tividale, Eng- Fia, 309. 
land. A, Calyx from one side. J ; raw ‘ 
B, Summit, showing mouth (m), anus Callocystites Jewetti, Hall. Silurian (Niagara Group); Lockport, 
(a), and three of the arms. The New York. A, Calyx from one side (natural size). #£, Ambulacral 
fourth arm (x) broken away, exposing grooves and three pectinated rhombs (rh), enlarged; 0, Mouth; 
flattened surface of calyx. an, Anus; g, Genital pore (after Hall). 
Family 8. Callocystidae. Bernard. 
Calyx composed of large plates arranged in three or four cycles, and exhibiting 
three to five pectinated rhombs, the component halves of which stand on contiguous plates, 
