316 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
Placiphorella stimpsoni Gould, 1859 
Proceedings of the Boston Society of Natural History , 7:165. Tryon and Pilsbry, 
Manual of Conchology , 14:307; PI. 62, figs. 84-87. 
T. tenuis, rotundato-ovata, depressa, fastigata, fusca, rufo, rosaceo 
viridi et flavo marmorata vel Iineata, concentrice striata; valvis angustis 
planatis; areis linea elevata finitis; valva antica parvula, crescentica; v. 
postica minima, emarginata. Ligamentum coriceum antice valde dilatatum, 
pilis fimbriatum. Long., 1.5; lat., 1 poll. (Gould.) 
Shell broadly oval, depressed, subangular, with straight side-slopes. 
Color whitish along the middle, the sides mottled and streaked with green¬ 
ish-yellow, olive and blue, the colors so blended as to give a general effect 
of dark olivaceous. Valves not beaked, sculptured with unequal growth¬ 
lines. Lateral areas having a moderately prominent diagonal rib, with an 
inconspicuous wider, lower, sutural rib, the space between excavated. 
Anterior valve narrowly crescentic, concentrically striated, but lacking all 
radiating sculpture. Posterior valve (figs. 84, 85) depressed, the mucro 
near the posterior margin, which is slightly and rather broadly waved 
inward. Interior a delicate blue-green tinted. Sinus a rather shallow, 
rounded wave in the earlier valves, becoming deeper, narrower, and angu¬ 
lar, in the eighth valve. Anterior valve having 8 slits, median valve having 
one slit on each side; the eaves narrow, tenaciously adhering to the girdle. 
Posterior valve small, its greatest width, including insertion and sutural- 
plates, measuring hardly more than one-half the width of the widest 
median valves; the short posterior insertion-plate rising from a very heavy 
callous rim; having one oblique slit on each side, and an almost imper¬ 
ceptible wave where the posterior sinus should be. Girdle rather narrow, 
brown, leathery, sparsely beset with spinules (the stumps only remaining 
in the specimen before me), of which there is one at each suture and a 
marginal fringe. (Tryon and Pilsbry, Manual of Conchology .) 
Type in United States National Museum, No. 1646. Type locality, 
Hakodadi Bay, Japan. 
Range. Bering Island, and on the east and south, to Cerros Island, 
Lower California. 
Placiphorella rufa Berry, 1917 
Proceedings of the California Academy of Sciences , series 4, 7:241; text figs. 3, 4. 
Shell of moderate size, broadly oval in outline, depressed. Dorsal ridge 
only moderately elevated, the side slopes little convex. Anterior valve 
crescentic, showing strong, irregular lines of growth and occasional weak 
traces of radial grooves. Median valves with the lateral areas raised into 
diagonal and sutural ribs having a groove-like depression between; other- 
[918] 
