40 THE NAUTILUS. 
Section Micromactra Dall. 
Hinge like the typical section, beaks sulcate, shell small. 
Mactra (Mactrotoma) californica Conrad, 1837. Fuca Strait to Central America, 
=WM. augusta Desh., 1854; +10 nasuta Auct. not Gould; not MM. 
californica Desh. 
Section Stmomactra Dall. 
Accessory lamellze free of the laterals. 
Mactra (Mactrotoma) dolabriformis Conrad, 1837. San Diego, Cal., to Guaymas, 
Mexico, 
Subgenus MacrreELra Gray, 1853. 
Section Mactrella ss. 
Surface of the valves smooth. 
Mactra (Mactrella) exoleta Gray, 1857. Gulf of Cal. to Guayaquil. 
+ Lutraria ventricosa Gould, 1851. 
Section Harvella Gray, 1853. 
Surface of the valves plicate. 
Mactra (Mactrella) elegans Sby., 1825. Panama to Gulf of Cal. 
+ WM. pacifica Conr., 1868. 
Genus SPISULA Gray, 1837. 
Type ©. solida L. Gray, 1847. 
Subgenus HemrmMactrRA Swainson, 1840. 
Section Mactromeris Conrad, 1868. 
Spisula (Hemimactra) polymyma Stm., 1860, var. alaskana Dall, 1894. Icey 
Cape to Neeah Bay. (See eastern list for synonymy). 
Spisula (Hemimactra) catilliformis Conr., 1867. Neeah Bay to San Diego, 
+-Standella californica Cpr., Auct., non Conr. 
Spisula (Hemimactra) Hemphillii Dall, 1894. San Diego. 
Spisula (Hemimactra) planulata Conrad, 1837. Monterey to San Diego, Not 
planulata of Cala. authors. 
Cay ae 
