132 AMERICAN MARINE CONCHOLOGY. 
Genus XYLOTRYA, Leach. 
Menke, Syn. Meth. 1830. 
1. X. FrmBriATA, Jeffreys. Figs. 295-297. 
Ann. and Mag. Nat. Hist., 3d ser. vi. 126. 
Shell subtrigonal, diameters about equal, strize on anterior area 
about thirty; posterior auricle large, sloping from the beak and 
descending much below the anterior triangle, inner face fan- 
shaped, large, overhanging, concave, concentrically striate. Pal- 
lets oar-shaped, the blade as long as the handle. 
Diam. 6 mill. Pallets 12 + mill. long. 
New Bedford, Mass., Fort Macon, N. C. 
The valves resemble those of J. navalis so closely that they 
are scarcely distinguishable from that species. The pallets are, 
however, entirely different. 
Family ANATINID&. 
Shell thin, generally inequivalve; interior nacreous; external 
surface granular; ligament external, thin; cartilage internal, 
placed in opposite pits and furnished with a free ossicle; muscu- 
lar impressions faint, the anterior elongated ; pallial line usually 
sinuated. 
Animal with mantle-margins united; siphons long, more or less 
united, fringed; gills single on each side, the outer lamina pro- 
longed dorsally beyond the line of attachment. 
Synopsis of Genera... 
Oval ; inequivalve, left valve deepest ; posterior side very short and con- 
tracted; beaks fissured, strengthened within by oblique diverging ribs ; 
hinge with a spoon-shaped process in each valve containing the cartilage 
and ossicle. PERIPLOMA, Schum. 
Subtriangular ; inequivalve, fragile; hinge having a narrow ledge within 
each valve, to which is attached the ligament and an adhering four-sided 
ossiculum. Lyonsra, Turton. 
Oblong; nearly equivalve, slightly compressed, attenuated, and gaping 
posteriorly, smooth or minutely scabrous ; cartilage processes thick, not 
prominent, with a crescentic ossicle. Turactia, Leach. 
Inequivalve, transverse, thin; valves close, attenuated behind; right valve 
flat, with a diverging ridge and cartilage furrows; left valve convex, 
with two diverging grooves at the hinge. PANDORA, Brug. 
