184 



ECHINODERMATA PELMATOZOA 



SUB-KINGDOM III 



pyramid ; arms unknown. Very abundant in the Ordovician of Russia and 



Scandinavia. E. aurantium, Rising, sp. 



Arachnocystites, Neumayr. Like the preceding, except 

 that it has strong arms, usually three in number, which 

 sometimes attain a length of 10 cm. Stem tapering distally 

 to a point. Ordovician (Etage D) ; Bohemia. A. infaustus, 

 Barr. sp. 



Caryocystites, v. Buch (Fig. 302). Calyx plates relatively 

 large. Pore-rhombs on external surface elevated, prominent. 

 Stem wanting. Ordovician ; Russia, Scandinavia, England. 



C ' 9natum, Wahlenb. 



Owciistites, Barrande. Ordovician (Etage D) ; Bohemia. 



, ... -T>MT n i T 



Palaeoct/stites, Billings. Calyx ovate or pyriform ; plates 

 numerous, and poriferous at the margins. Ordovician ; 

 Canada. 



grana- 



turn, wahib. sp. Or- 



dovician ; Oeland. 



Plates of the natural 

 elevated 



Calyx composed of 

 regularly arranged plates, 

 attachment of small arms. 

 to Permian. 



Family 5. Cryptocrinidae. Zittel. 



rings of very finely perforate or imperforate, somewhat 

 Mouth central, surrounded by articular facets for the 

 Anus eccentric; stem round and slender. Ordovician 



Cryptocrinus, v. Buch (Fig. 303). Base composed of three plates, and sur- 

 mounted by two zones, each containing five plates of unequal sizes. Mouth 

 and anus enclosed within a 

 ring of smaller pieces. Ordo- 

 vician ; St. Petersburg. C. 

 cerasus, v. Buch. 



Echinocystites, Hall. Or- 

 dovician ; North America. 



Porocrinus, Bill. (Fig. 

 304). Base composed of 

 three plates, and succeeded 

 by two circlets of regularly 

 alternating pieces. Upper 



Cycle giving rise to five 



feeble, uniserial arms. Small 



from above, and from below 



FIG. 303. 

 Cryptocrinus cerasus, v. Buch. 



fur- 



a, Porocrinus conicus, Billings. 

 Ordovician ; Ottawa, Canada. 

 Nat. size (after Billings) ; 6, P. 

 riiilicitus, Beyr. Ordovician ; St. 

 Petersburg. Calyx plates show- 

 ing pectinated rhombs. Consider- 

 ably enlarged (after Beyrich). 



supplementary pieces _- (nat size); m>Mouth . fl> Anus 

 nished with pore-rhombs in- 

 tercalated in the re-entrant angles between the calyx plates. Ordovician ; 

 Canada, Russia. 



Hypocrinus, Beyr. Base composed of three plates, and succeeded by two 

 zones of alternately arranged, perforate plates. Mouth central. Permian ; 

 Timor. 



Family 6. Oaryocrinidae. Bernard. 



Calyx composed of a moderate number of plates exhibiting a more or less definite 

 arrangement in cycles. Certain or all of the side plates with pore-rhombs ; those of 

 the ventral surface imperf orate. Arms three to thirteen, free, feeble. Stem constantly 

 present, occasionally long. Ordovician and Silurian. 



