40 
THE NAUTILUS. 
Section Micromactra Dali. 
Hinge like the typical section, beaks sulcate, shell small. 
Mactra (Mactrotoma) californioa Conrad, 1S37. Fuca Strait to Central America. 
—M. augusta Desk., 1854 ; 4 -M. nasuta Auct. not Gould ; not M. 
californica Desk. 
Section Simomactra Dali. 
Accessory lamellte free of the laterals. 
Mactra (Mactrotoma) dolabriformis Conrad, 1837. San Diego, Cal., to Guaymas, 
Mexico. 
Subgenus Mactrella Gray, 1853. 
Section Mactrella ss. 
Surface of the valves smooth. 
Mactra (Mactrella) exoleta Gray, 1837. 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. 
4- M. pacifica Conr., 1868. 
Genus SPISULA Gray, 1837. 
Type M. solida L. Gray, 1847. 
Subgenus Hemimactra Swainson, 1840. 
Section Mactromeris Conrad, 1868. 
7 a. ’ 
Spisula (Hemimactra) polymyma Stm., 1860, var. alaskana Dali, 1894. Icy 
Cape to Neeah Bay. (See eastern list for synonymy). Is2-C 0 & 
Spisula (Hemimactra) catilliformis Corn-., 1867. Neeah Bay to San Diego. 
-\-Standella californica Cpr., Auct., non Conr. 
Spisula (Hemimactra) Hemphillii Dali, 1894. San Diego. 
Spisula (Hemimactra) planulata Conrad, 1837. Monterey to San Diego. Not 
planulata of Cal a. authors. 
