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are attached to rocks and become quite massive like Spojidyhis. For con- venience, we are considering it a full genus. Himjttes multirugosiis Gale Giant Rock Scallop Plate 29a Aleutian Island to Lower California. Up to 8 inches in length. A heavy massive shell characterized by the early "Chlamys-Hke" shell at the beaks. Interior white with a purplish hinge area. Attached to rocks by the right valve. The ^2-inch long young are almost impossible to separate from some species of Chlainys, except when they show a mauve spot on the inside of the hinge line on each side of the resilium pit, or if they show signs of distortion or a mottling pattern of color on the outside of the valves. Some vouno- are bright-orancre. A common species. Formerly known as H'mnites gigante7is Gray. This is a regrettable name change which I have followed, since leading workers on the Pacific Coast have adopted it. Fa77nly PROPEAMUSSIIDAE Genus Propeaviusshmi Gregorio 1883 Propeavitissmm poiirtalesiaimm Dall Pourtales' Glass Scallop Plate 27c Southeast Florida and the West Indies. /4 inch in length. Valves very slightly convex. Shell extremely thin and transparent (hke thin mica flakes). Each valve reinforced inside with about 9 rod-like, opaque 'hite ribs. Exterior of one valve is smoothish, the other valve with numerous, microscopic, concentric threads. Common off- shore. Frequently dredged off Aliama by amateurs. There have been a number of other species described, some of which may only be forms of this variable species. Fmjiily SPONDYLIDAE Genus Spondylus Linne 1758 Spondylus americanus Hermann Atlantic Thorny Oyster Plate 36b South half of Florida and the West Indies. 3 to 4 inches in size. Spines 2 or less inches in length, usually standing fairly erect. Color variable: white with yellow unbones, red or purple; sometimes all rose, all cream or all pink. The young are much less spinose, and might be confused with Chama which, however, does not have the ball- and-socket type of hinge. Beautiful and large specimens are found clinging