184 ECHINODERMATA—PELMATOZOA SUB-KINGDOM III 
pyramid; arms unknown. Very abundant in the Ordovician of Russia and 
Scandinavia. £. aurantium, Hising. 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. 
Caryocystites grana. C- granatum, Wahlenb. 
twm, Wahlb. sp. Or- Orocystites, Barrande. Ordovician (Etage D); Bohemia. 
dovician ; Oeland. ° ae E 
Plates of the natural Palaeocystites, Billings. Calyx ovate or pyriform; plates 
size showing elevated ein aa ° 4 
orca nibs: numerous, and poriferous at the margins. Ordovician ; 
Canada. 

Family 5. Cryptocrinidae. Zaittel. 
Calyx composed of three rings of very finely perforate or imperforate, somewhat 
regularly arranged plates. Mouth central, surrounded by articular facets for the 
attachment of small arms. Anus eccentric ; stem round and slender. Ordovician 
to Permian. 
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 Fre, 303. omlovicien; Ottawa, Cate 
cycle giving rise to five Cryptocrinus cerasus, v. Buch. Nat. size (after Billings); }, P. 
feebl iserial ar ll Ordovician ; Pulkowa, Russia. radiatus, Beyr. Ordovician ; St. 
eeble, uniserlal arms. Sma a, b, c, Calyx from one side, Petersburg. Calyx plates show- 
7 . from above, and from below ing pectinated rhombs. Consider- 
supplementary pieces fur- (nat. size); m, Mouth; a, Anus. ably enlarged (after Beyrich). 
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. 

Fia. 304. 
Family 6. Caryocrinidae. 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 imperforate. Arms three to thirteen, free, feeble. Stem constantly 
present, occasionally long. Ordovician and Silurian. 
