National Geographic : 1949 Jul
©National Geographic Society 50 K tachruiomeby Iutherford Platt Unlike Its Swimmer Cousin, the Pecten, the Thorny Oyster Lives Cemented to Coral Rock There are 85 known species but comparatively few types in this bivalve family. Strangely, the smaller speci mens have longer spines than the larger. The average size is four to eight inches across. Holding the valves together and acting as a hinge, each has two interlocking teeth. Pictured here are two Chliamt,. ( 1 ) congr'egata and (11) lazarus; and nine Spondylus: (2) ducalis (Philippines); (3. 4, 5) dominicensis (Key West); (6) japonicus (Japan); (7) princeps (Mazatlan, Mexico); (8) aurantium (Philippines); (9) dominicensis (Tarpon Springs, Florida); (10) acicularis (Philippines).