190 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
Siliqua patula Dixon, 1788. 
Plate 48, fig. 1, and plate 52, fig. 1. 
Dixon's Voy., p. 355, fig. 2. 
This is a thin, brittle shell, smooth within and without; one valve 
furnished with two front and two lateral teeth; the other has one front and 
one side tooth, which slip in between the others in the opposite valve: from 
the tooth, in each valve, proceeds a strong rib, which extends to above 
halfway across the shell, and gradually loses itself toward the edge, which 
is smooth and sharp. The colour of the outside is white, circularly, but 
faintly, zoned with violet, and is covered with a smooth yellowish-brown 
epidermis, which appears darkest where the zones are: the inside is white, 
slightly zoned and tinted with violet and pink. (Dixon.) 
Type in Swainson Collection. Type locality, Cook's River, N. W. Coast 
of America. 
Range. Okhotsk Sea to Sitka, Alaska. 
Siliqua patula alta Broderip and Sowerby, 1829. 
Plate 47, figs. 1, 2. 
Zool. Jour., 4:362. 
Testa albido-carnea, subovata, alta, antice rotundata, postice, epider- 
mide fusca, extra marginem extensa. Long., 4% 0 ; lat., %o J alt., 
2%o- (Broderip and Sowerby.) 
Type in British Museum? Type locality, Arctic Ocean. 
Range. Bering Strait to Kodiak Island, Alaska. 
Siliqua patula nuttallii Conrad, 1837. 
Plate 18, figs. 2a, 2b. 
Jour. Acad. Nat. Sci. Phila., 7:232; pi. 17, fig. 9. 
Shell oblong-oval, thin, fragile, compressed; posterior margin more 
obtusely rounded than the anterior; color white, obscurely rayed; epi¬ 
dermis horn-color, with paler spots; beaks purple; cardinal teeth two in 
the right valve, lamellar, remote; in the right valve four; ribs broad, 
oblique. Length, 4inches. (Conrad.) 
Type locality, Point Adams in the estuary of the Columbia. 
Range. Lituya Bay, Alaska, to Monterey, California. 
Family MACTRID7E. 
Genus LABIOSA (Schmidt) Moller, 1832. 
Shell oblong, widely gaping and reflected posteriorly; posterior slope 
narrow, defined by a carina; lateral teeth distinct, the anterior one oblique, 
