My Dear Sir —As something towards enabling amateur and other geologists to communicate some of the results of their researches to their fellow-inquirers, I beg to offer the enclosed directions for making a preparation of gutta-percha and bees-wax, much better adapted for taking casts and moulds of fossils than gutta-percha itself; and also some useful remarks for the preparation of plaster-casts. These directions have been chiefly drawn up, at my request, by my friend, Mr. John Wetherell, of Highgate. I have also to observe that the prepared gutta-percha is capable of being applied to the purposes of the museum in another way, which has been suggested to me by a friend lately. Thus, have some narrow slips of tin folded into squares, of convenient sizes, and into these press some of the composition, and use these as pedestals for such fossil shells, and other specimens, as will not stand steadily by themselves. By warming these pedestals in hot water, they are readily softened so as to receive the fossils when pressed into them, and the latter can be at any time raised for examination.

Of course this composition, or even gutta-percha itself, is unfit for use in hot climates, and for transmission, by post or otherwise, to the tropics.

Of all the wondrous changes which nature has wrought on the earth's crust, there is scarcely anything that will bear comparison with those which meet the eye of the traveller in volcanic regions. Of the two great agents in. Geological transformation—water and fire, the one moves us with admiration at the delicacy of its operations, the other strikes us with awe at the mightiness of its influences, and the rapidity of its work.

Few, if any, countries present ua with such remarkable or various manifestations of the potency of subterranean heat as Iceland. So much so, indeed, that it appears as though it were the acknowledged safety-valve, in this portion of our globe at least, through which the troubled contents of depths unknown may, on any emergency, find a ready vent.

Interest more than ordinary appears to have been taken of late in this most remarkable region. No less than six parties of tourists having, during the year before last, investigated the natural marvels of the island. One of these adventurers, Lord Dufferin, in a most interesting and amusing book, has given to the world a record of his travels. From his “Letters from High Latitudes” we propose to quote his graphic picture of the result of volcanic action, in producing a very remarkable and very manifest change in the aspect of the large tract of country to which that portion of hiB narrative refers.

But before we proceed to this, it may perhaps be useful to recal to the reader's recollection the two theories which have, up to the present time, been put forth with respect to the causes of internal heat, and hence to the origin of volcanic action in general.

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.