Page:American Seashells (1954).djvu/566

Shell similar to that of T. navalis, but smaller, more finely sculptured and transparent, and with numerous, closely set ridges. Pallets: blade with an oval, calcareous base, surmounted by a horny cap, amber to black in color. The horny portion is commonly deeply excavated at the tip, but may be cut off bluntly. The two elements of the blade come apart very easily. T. toivnsendi Bartsch is the same according to Kofoid and others. Suborder ANOMALODESMACEA Siiperjamily PANDORACEA Family LYONSIIDAE Genus Lyonsia Turton 1822 Lyonsia hyalina Conrad Glassy Lyonsia Plate 28U Nova Scotia to South Carolina. % to % inch in length; very thin and fragile. Semi-translucent and whitish to tan. Shell elongate, with the anterior end somewhat obese and the posterior end tapering and laterally compressed. Without teeth in the weak hinge, but with a small, free, elongate, calcareous ossicle inside just under the small, inflated, anteriorly pointing beaks. Periostracum very thin, with numerous raised radial lines. Commonly has tiny sand grains attached. Common from low water to 34 fathoms. LyoJisia hyalina floridana Conrad, known from the west coast of Florida to Texas, is very similar, differing only in being % as high as long (instead of /4) and in having a narrower, more rostrate posterior end. Common. Lyonsia arenosa Moller Sanded Lyonsia Greenland to Maine. Alaska to Vancouver. ^ to % inch in length, resembling hyalina, but much less obese, with a heavier, greenish-yellow periostracum, and with its posterior end more oval and higher than the anterior end. The dorsal margin of the right valve behind the beak overlaps that of the left valve considerably. There is no posterior gape as in hyalina. Like other species in the genus, it glues sand grains to itself. Moderately common from low water to 60 fathoms. Lyonsia calif ornica Conrad California Lyonsia Puget Sound to Lower California. I inch in length, very thin, fragile and almost transparent. Quite elongate and moderately obese. Beak area swollen. Posterior end tapering and later-