21:0699 Genus Amiantis Cpr., 1863. 
Tryon treated this as a subgenus of Cytherea, saying that it 
only differs in having the fulcra thicker than most RtReE species, 
and rugose. 
21:0700 Amiantis callosa Conr. 118. 764. 
Santa Barbara, Cal., to Gulf of Tehuantepec, Mexico. Dall : 
gives this generic rank. 
21:0701 Genus Antigona Schumacher, 1817. 
Treated by Tryon as a synonym of Venus, by Dall as a valid 
genus. 
21:0702 Antigona fordi (Yates). 
Monterey, bay Cal., to Baja Cal., and Panama? Described 
under Venus (see 351, 1158, 2158). 
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21:0703 Genus Barnea (Leach) Risso, 1826. 
Shell oval-oblong; anteriorly gaping; a single lanceolate 
dorsal accessory valve; umbonal process reflexed, closely applied. 
21:0704 Barnea pacifica Stearns, 1871. | 
San Francisco bay, Cal., to Baja Cal. Described under 
Pholas (982). 
21:0705 Genus Crenella Brown, 1827. 
Shell oval or rhomboidal, nacreous, cancellated; umbones 
straight, ligament small, hinge of each valve furnished with an 
upright tooth, which is crenulated, as well as the hinge-plate. 
21:0706 Crenella leana Dall, 1897. Alaska. 
21:0707 Crenella grisea Dall, 1867. Alaska. 
21:0708 Crenella divaricata Orbigny, 1847. 
Santa Barbara Islands, Cal., to Panama bay; West Indies. 
21:0709 Genus Oryptomya Conrad, 1848. 
Shell inequilateral, transverse, oblong, gaping behind; valves 
with radiating striae, sometimes crossed by concentric lines; 
right valve with a lamellar tooth, left valve with a broad fosset; 
ligament internal; pallal impression with a small sinus. Siphons 
short; not covered with a coriaceous epidermis, as is the case in 
Mya, 
21:0710 Oryptomya californica Conrad, 1837. 102. 
Chichagoff Island, Alaska, to Topolobampo, Mexico. 102 
(1184). Sphenia californica Conrad, is a synonym. 
21:0711 Genus Cyathodonta Conrad, 1849. 
Shell like Anatina in form; hinge with a broad, not very 
projecting fosset, which is carinated near the margin; muscular 
impressions rounded, indistinct; pallial impression with a large, 
rounded sinus. - 
21:0712 Cyathodonta dubiosa Dall, 1915. 
San Pedro, Cal., to Gulf of Cal. 
21:0713 Cyathodonta pedroana Dall, 1915. 
San Pedro Bay and Catalina Island, Cal. 
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