. The animals and man; an elementary textbook of zoology and human physiology. Zoology; Physiology. 174 THE ANIMALS AND MAN The extent of the acreage of the American oyster-beds is larger than that of any other country. "The Baltimore oyster-beds on the Chesapeake River and its tributaries cover 3,000 acres, and produce an annual crop of 25,000,000 ; The "pearl-oyster" is not a true oyster, that is, not a member of the family to which the edible oysters belong, but it is a member of the same class, that is, it is a bivalve. Fig. 85. Pholas sp., a mollusc burrowing i
. The animals and man; an elementary textbook of zoology and human physiology. Zoology; Physiology. 174 THE ANIMALS AND MAN The extent of the acreage of the American oyster-beds is larger than that of any other country. "The Baltimore oyster-beds on the Chesapeake River and its tributaries cover 3,000 acres, and produce an annual crop of 25,000,000 ; The "pearl-oyster" is not a true oyster, that is, not a member of the family to which the edible oysters belong, but it is a member of the same class, that is, it is a bivalve. Fig. 85. Pholas sp., a mollusc burrowing in sandstone. (Photograph by C. H. Snow; permission of the American Society of Civil Engineers.) mollusc. Pearls are obtained from a number of different "pearl-oysters," but the finest pearls and mother-of-pearl come from the tropical species Meleagrina margaritifera, This pearl-oyster has an extensive distribution, being found in Madagascar, the Persian Gulf, Ceylon, Austraha, Philippine Islands, South Sea Islands, Panama, West Indies, etc. Mother-of-pearl is simply the inner lining of the shell, which is composed of numerous thin layers of carbonate of lime so arranged that the edges of the suc- cessive layers produce many fine strias very close together. The beautiful iridescence of this inner shell-lining is caused. by the complicated diffraction and reflection (interference effects) of the light by the fine striae and the translucent. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Kellogg, Vernon L. (Vernon Lyman), 1867-1937; McCracken, Mary Isabel. New York, H. Holt and Company
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