the whole history inconsistent with the supposition that these observations really relate to a River Crab of the family Potamonidæ, of which at least one species, _Pseudothelphusa dentata_, is known to occur on the island of St. Vincent. As we have already seen, some of these River Crabs are quite as much land animals as the Gecarcinidæ, and they are known to have a direct development. [3] I am indebted to Mr. J. T. Cunningham for calling my attention to some of the facts here recorded. The Gecarcinidæ possess well-developed gills, but in addition the gill chambers are modified for air-breathing, as in some other amphibious Crabs (_Ocypode_, _Gelasimus_, etc.). Each chamber is capacious and vaulted, and the lining membrane is thick and richly supplied with bloodvessels, and is folded so as to divide off the upper part of the chamber as a sort of pocket. The Land Hermit Crabs of the family Coenobitidæ are found on the coasts of all tropical seas. Like the Gecarcinidæ, they visit the sea periodically for the purpose of hatching off the eggs, and the larval stages are marine. The species of the genus _Coenobita_ (Plate XXVI.) resemble the marine Hermit Crabs in general shape, and like them use the shells of Gasteropod Molluscs as portable shelters. Where shells are scarce, other hollow objects are occasionally utilized; for example, large individuals will sometimes carry about the shell of a broken coconut, and a specimen has been seen to walk off in a cracked test-tube discarded by a naturalist who was investigating their habits. In one instance Professor Alcock saw an individual "so big that it seemed to have given up hope of finding a house, and was wandering about recklessly, with its tail behind it all unprotected." The Coenobites often climb into bushes in search of food, and Dr. Alcock "once found one of them busy, like a large bee, among the florets of a coconut, which made me wonder whether they may not sometimes play a part in fertilizing flowers." They are, however, by no means exclusively vegetarians. The author just quoted describes a visit to Pitti Bank in the Laccadive Archipelago, the breeding-ground of two species of terns. The ground was everywhere strewn with the dead bodies and clean-picked skeletons of the young birds. "We soon discovered that one great cause of the wholesale destruction of young birds was the voracity of swarms of large Hermit Crabs (_Coenobita_), for again and again we found recently killed birds, in all the beauty of their first speckled plumage, being torn to pieces by a writhing pack of these ghastly Crustaceans. There were plenty of large Ocypode Crabs, too (_O. ceratophthalmus_), aiding in the carnage." On Christmas Island Dr. Andrews found a species of _Coenobita_ not unfrequently in the higher parts of the island far from the sea, and he remarks that the occurrence of large marine shells high up on the hills seemed very puzzling until it was noticed that they were brought by the Hermit Crabs.