The crinoids, which in this paper I bring under notice, belong to two new genera, which I have designated, the one by the name of Hydreionocrinus (ὑδρϵῖον, a watering-pot), from the resemblance to the rose of a watering-pot of the head of the species referred to, and the other by the name of Pisocrinus (πίσον, a pea). I begin with the exposition of the character of these new genera, and will afterwards describe the species which belong to them, and in doing this I shall make use of the same technical terms as I have done in my other works upon the crinoids.

Genus.—Hydreionocrinus, De Koninck.

Synonyms.—Poteriocrinus (in part), Phillips, 1836, “ Geol. of York,” Vol. II., p. 204.

Cupressocrinus, M'Coy, 1849, Ann. Nat. Hist.,” 2 ser., Vol. II., p. 22 4; non Goldfuss.

Poteriocrinus, De Kon., 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 × 5, of which one reposes directly on one of the sub-radials; Brachial, or arm-plates, 5 × 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.