196 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
Type. Lutraria nuttallii Conrad, 1837. 
Distribution. West coast of North America. 
Schizothaerus nuttallii Conrad, 1837. 
Plate 31, figs, la, lb. 
Jour. Acad. Nat. Sci. Philo,, 7:235; pi. 18, fig. 1. U. S. Fish Comm. Bull., 3, No. 
23:354, fig. 1. 
Shell elliptical, slightly gibbous from beak to base; posterior side 
produced; ligament margin slightly declining; rectilinear, extremity 
obliquely sub-truncated, umbo prominent; colour white; epidermis very 
thin, brown, wrinkled on the margin. Length, 6 inches. (Conrad.) 
Type locality near Santa Barbara, California. 
Range. Wrangell, Alaska, to San Diego, California. In the Pleisto¬ 
cene at Santa Barbara and San Diego, and the Pliocene at Santa Barbara, 
California. 
Schizothaerus nuttallii capax, Gould, 1850. 
Proc. Boston Soc. Nat. Hist., 3 :217. Conch. Iconica, Mactra; pi. 1, fig. 4. 
Testa magnifica, ventricosa, ovato-rotundata, antice rotundata, postice 
subtriangularis, truncata, valde hians, concentrice undulato-striata, epi- 
dermide luteo-viridi (post costam medianum radiatim corrugato) induta; 
umbonibus tumidis, incubentibus, attigentibus: cardo validus; fovea lata, 
obliqua triangulari; dente cardinali crasso, erecto, plicato, basi appendi- 
culato; dentibus lateralibus compressis, conspicuis. Interior calcarea; sinu 
siphonali linguiformi, dimidam longitudinis testae attigente. Long., 5^; 
alt., 4; lat., 3 poll. (Gould.) 
No other species approaches this in size and capacity. (Gould.) 
Shell very largely inflated, ovately sub-rhomboidal, inequilateral, trans¬ 
versely striated and rough, whitish, covered toward the margin with a 
black-brown epidermis, anterior narrowly gaping, posteriorly very broadly 
gaping; umbos large, obtuse, approximated; siphons of the mantle broad, 
deep, horizontal. (Conch. Iconica.) This is the description given by 
Middendorff, but he called it Lutraria maxima, and gives the habitat as 
California. 
Type locality, Puget Sound. 
Range. Kodiak Island, Alaska, to San Pedro, California. 
FAMILY MESODESMATID^E. 
Genus ERVILIA Turton, 1822. 
Shell minute, oval, close; cartilage in a central pit; right valve with a 
single prominent tooth in front and obscure tooth behind; left valve with 
