468 Afiierican Seashells 



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- 



