Writing in 1820, John Crawfurd stated that the annual export of pearls from Sulu Islands to China approximated 25,000 Spanish dollars in value, and the mother-of-pearl similarly exported was worth 70,000 dollars. “Considering the turbulent and piratical habits of the natives of the Sulu group, it is certain that a greater share of skill and industry than can at present be applied to the fisheries, would greatly enhance the value and amount of their produce.”[266] In the Sulu Archipelago, the pearl-oyster reefs exist from Sibǔtu Pass to Basilan Strait, and roughly cover an estimated area of 15,000 square miles; that is, in the most favorable localities throughout this area, pearl-oysters occur to a greater or less extent. The fisheries are prosecuted by Malays and Chinese, and are largely centered at Sulu. Pearl-oysters occur about many other islands. They exist at Maimbun and Parong; and also off the island of Tapul and its neighbor Lagos, both southwest of Maimbun. In the channels among these islands, on the rocky gravelly bottom where there is a good current, oysters are commonly found. They also occur off Laminusa, northeast of Tawi-Tawi, at Cuyo Island, and in the waters about Malampaya and Bacuit. The large mother-of-pearl oyster (_Margaritifera maxima_) known locally as _concha de nacr_, is by far the most abundant. When full-grown in this region it is ordinarily between ten and thirteen inches in diameter. The young oyster attaches itself to the bottom by means of the green byssus; but after attaining a weight of one pound, it is too heavy to be easily moved by the tide, and the ligature gradually disappears. The Australian “black lip” (_Margaritifera margaritifera_), known here as _concha de nagra_, is also found. In these waters it attains a diameter of about eight inches, but most specimens are considerably smaller. There is another pearly shell in the Philippines, a spiral gasteropod known locally as _caracoles_, which is ordinarily five or six inches in diameter, and has a beautiful pearly surface. This yields very few pearls; it is sought for pearl-button manufacture, selling for about the same as the _concha de nagra_. Streeter states that it is declared by the natives of the Sulu Archipelago that pearls of a yellowish hue have been found in the pearly nautilus (_Nautilus pompilius_), one of the group of cephalopodous mollusks. As, however, there is a superstition that they bring ill luck, the natives say that they throw them away, believing that any one who should fight while wearing one of these pearls in a ring, would certainly be killed. If we consider the habits and organism of this remarkable animal, and the splendid nacreous coating of its shell, the assertion that pearls are found in it seems quite natural. Indeed, the occurrence of pearls in the pearly nautilus is generally recognized.