The character of this pearl is extreme whiteness, and even in this whiteness Pliny justly says there are shades or differences. To continue to use his words, the clearest of these are found in the Red Sea, but those in India have the colour of the flakes, or divisions of the lapis specularis. The most excellent are those like a solution of alum, limpid, milky like, and even with a certain almost imperceptible cast of a fiery colour. Theophrastus says, that these pearls are transparent, as indeed the foregoing description of Pliny would lead us to imagine; but it is not so, and if they were, it is apprehended they would lose all their beauty and value, and approach too much to glass. It has been erronenously said, that pearl shells grow upon rocks, and again, that they are caught by nets. This is certainly a contradiction, as nobody would employ nets to gather fish from among rocks. On the contrary, all kinds of pearl are found in the deepest, stillest water, and softest bottom. The parts of most of them are too fine to bear the agitation of the sea among rocks. Their manners and œconomy are little known, but, as far as I have observed, they are all stuck in the mud upright by an extremity, the mussel by one end, the pinna by the small sharp point, and the berberi, or lule, by the hinge or square part which projects from the round. In shallow and clear streams I have seen small furrows or tracts, upon the sandy bottom, by which you could trace the mussel, from its last station, and these not straight, but deviating into traverses and triangles, like the course of a ship in a contrary wind laid down upon a map, the tract of the mussel probably in pursuit of food. The general belief is, that the mussel is constantly stationary in a state of repose, and cannot transfer itself from place to place. This is a vulgar prejudice, and one of those facts that are mistaken for want of sufficient pains, or opportunity, to make more critical observation. Others finding the first opinion a false one, and that they are endowed with power of changing place like other animals, have, upon the same foundation, gone into the contrary extreme, so far as to attribute swiftness to them, a property surely inconsistent with their being fixed to rocks. Pliny and Solinus say, that the mussel have leaders, and go in flocks, and that their leader is endowed with great cunning, to protect himself and his flock from the fishers, and when he is taken, the others fall an easy prey. This however I think we are to look upon as a fable. Some of the most accurate observers having discovered the motion of the mussel, which is indeed wonderful, and that they lie in beds, which is not at all so, have added the rest to make their history complete.