194 AMERICAN MARINE CONCHOLOGY. 
Doubtful Species. 
O. semicylindrica, Say. This appears to be an immature shell 
and is not identified. It is said to inhabit the coast of Georgia 
and Florida, imbedded in sponges. 
Genus ANOMIA, Linnzus. 
Syst. Nat., edit. xii. 1150. 1767. 
Animal with the mantle open, its margins with a short double 
fringe ; lips membranous, elongated ; palpi fixed, striated on both 
sides; gills two on each side, united posteriorly, the outer laminz 
incomplete and free; foot small, cylindrical, subsidiary to a 
lamellar and more or less calcified byssal plug, attached to the 
upper valve by three muscles ; adductor muscle behind the byssal 
muscles, smal!, composed of two elements ; sexes distinct; ovary 
extending into the substance of the lower mantle-lobe. 
There are about twenty species ; distribution principally in tem- 
perate seas, from low water to 100 fathoms. 
1. A. GuaBRA, Verrill. Fig. 534. 
Am. Journ. Sci., 288. April, 1872. 
A. ephippium, Gould. Invert. Mass., edit. i. 1841. 
A. electrica, Gould. Invert., edit. ii. 205. 1870. 
Shell orbicular, or distorted ; surface scaly, lamellar, and easily 
impressed by contact with other shells, etc.; upper valve very 
convex, with a small beak; lower valve smaller, flat, or concave, 
with a circular byssal hole, which is united to the margin by a 
greater or less fissure. Polished, and varying in color from black 
through red, yellow, and ash to white; the same colors internally, 
except that the muscular impression is opaque white. 
Diameter usually about 1 inch. 
Cape Cod, Mass. to Florida. 
This is our common Anomia, generally known as A. ephippium, 
but it appears to be distinct from the European shell bearing that 
name. 
9. A. ACULEATA, Gmelin. Figs. 535, 536. 
Syst. Nat., 3346. 1790. 
Shell small, rounded ; upper valve with fine, prickly scales ar- 
ranged in radiating lines; lower valve smooth; yellowish or 
whitish. 
Diameter about half an inch. 
Eastport, Maine, northwards. 
