KONINCK — NEW PALAEOZOIC CRINOIDS. 
147' 
the same technical terms as I have done in my other works upon the 
crinoids. 
Genus. — Hydreionocrinus, De Koninck. 
Synonyms. — Poteriocrinus (in part), I'hillips, 1836, " Gcol. of York," 
Vol. II., p. 204. 
Ciiprcssocrinua, M'Coy, 1849, Ann. Nat. Hist.," 2 ser.. 
Vol. II., p. 22 4 ; non Goldfuss. 
Poteriocrinus, Be Kon., 1854, " Recherclies snr leg 
Crinoides," p. 90. 
Generic Formula. — Basal plates 5, Sub-radial plates 5, of which three are of the 
same form, the fourth serving as a base to one radial, and the fifth welded to two 
anals ; Anal -plates 5 ; Radial plates 2 x 5, of which one reposes directly on one of 
the sub-radials ; Brachial, or arm-plates, 5 x 10, giving rise to 20 arms, welded 
together, and composed of alternating articulations, to the number of 18 or 20, 
and surmounted by a circle composed of 15 fusiform pieces, joined to each other. 
Vault or dome, composed of a great number of little pentagonal or hexagonal 
pieces. Stem with cylindrical articulations. 
In comparing this formula with that of the genus Poteriocrinus, it 
will be easy to perceive the analogy between them. Indeed, in both 
genera, one observes five basal plates, which by their junction foim a 
