KONINCK — NEW PALAEOZOIC CRINOIDS. 



147 



the same technical terms as I have done in my other works upon the 

 crinoids. 



Genu^. — Hydreionocrinus, De Koninck. 



Synonyms. — Poteriocrinus (in part), Phillips, 1836, " Geol. of York," 

 Vol. 11. , p. 204. 



Cupressocrinus, M'Coy, 1849, Ann. Nat. Hist.," 2 ser., 

 Yol. II., p. 22 4 ; non Goldfuss. 



Poteriocrinus, Be Eon., 1854, Recherches sur les 

 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 form a 



