194 AMERICAN MARINE CONCHOLOGY. 



Doubtful Species. 



0. 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, Linnaeus. 

 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 laminae 

 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, small, 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. GLABRA, Yerrill. 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. 



2. 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. 



