Pearls: Fisheries, Red Sea, India, Bedouin, Shells Page 262



	PEARL FISHERIES

	bring about twice as much, muckets half that price, and the other varieties together will average about twenty-five per cent, more than nigger-heads, though among these the deer-horn is worth about four times as much as the nigger-head. In the first six months of 1898 nearly four thousand tons of mussel shells were sold by mussel fishermen on the Mississippi. They brought about thirty-nine thousand dollars, 94 per cent, of these were nigger-heads. The spawning time of the unio varies with different species. In the central Mississippi basin it is normally February, March and April for nigger-head, and summer and early fall for the mucket and sand-shell. The unio is a slow growing animal. Under normal conditions it takes ten years for a nigger-head to reach a size of three inches; fifteen to eighteen years to attain a shell diameter of 4^ inches. This corresponds very closely with the life of the meleagrina, though the shell of the latter ceases to grow in size at about eight or ten years. After that it continues to lay on thickness up to eighteen or twenty years. 271