Note 147 — Genus—ALCIPPE. Pl. 22, 23.

I have given some remarkable cases in my volume on ‘Volcanic Islands,’ (p. 49), in which limestone, having almost the hardness and specific gravity of marble, has been thus deposited. Almost every coral-reef offers similar examples. The curious substance described by Mr. Horner and Sir David Brewster, (‘Philosoph. Transact.,’ 1836, p. 65), which is formed during the manufactory of cloth, offers another example of the strong tendency which lime and animal matter have to unite. Lately, Dr. Horsford, in ‘Silliman’s North American Journal,’ Jan. 1853, has discussed the chemical theory in an analogous case on the coast of Florida; he attributes the aggregation to the formation of a hydrate of lime through the action of the animal matter. Mr. G. B. Sowerby, Junr., has described a case very analogous to that of Alcippe, (‘Proceedings of Zoolog. Soc., Mollusca,’ Pl. 5, fig. 4, p. 162, 1850), namely, that of Pholas calva, in which a tube is formed of inorganic calcareous matter, serving to narrow the entrance.