The Bernhard Crab has been proved to have the power of dissolving shells, it not being unusual to find the long fusiform shells which are inhabited by these animals with the inner lip, and the greater part of the pillar on the inside of the mouth, destroyed, so as to render the aperture much larger than usual. Dr. Gray is quite convinced that these Crabs have the above power, some to a much greater degree than others. Certain Crabs, especially in the West Indies, are almost exclusively terrestrial, visiting the sea only at given periods, for the deposition of their eggs. These Crabs carry in their gill-chambers sufficient water for the purpose of respiration; they live in burrows, and traverse considerable tracts of land in the performance of their migratory journeys. Of these, some, as the Violet Crab, are exquisite delicacies. Of a great Crab migration we find these details in the "Jamaica Royal Gazette:"--In 1811 there was a very extraordinary production of Black Crabs in the eastern part of Jamaica. In June or July the whole district of Manchidneed was covered with countless numbers, swarming from the sea to the mountains. Of this the writer was an eye-witness. On ascending Over Hill from the vale of Plantain Garden River, the road appeared of a reddish colour, as if strewed with brick-dust. It was owing to myriads of young Black Crabs, about the size of the nail of a man's finger, moving at a pretty quick pace, direct for the mountains. "I rode along the coast," says the writer, "a distance of about fifteen miles, and found it nearly the same the whole way. Returning the following day, I found the road still covered with them, the same as the day before. How have they been produced, and where do they come from? were questions everybody asked, and nobody could answer. It is well known that Crabs deposit their eggs once a year, in May; but, except on this occasion, though living on the coast, I had never seen above a dozen young Crabs together; and here were myriads. No unusual number of old Crabs had been observed in that season; and it is worthy of note, that they were moving from a rock-bound coast of inaccessible cliffs, the abode of sea-birds, and exposed to the constant influence of the trade winds. No person, as far as I know, ever saw the like, except on that occasion; and I have understood that since 1811 Black Crabs have been more abundant further in to the interior of the island than they were ever known before."