424 



MARINE INVERTEBRATES 



junctures are so slight that they break readily when a specimen 

 of a gill is handled, leaving the filaments free. The presence of a 

 byssal gland in the foot, and often a well-developed byssus, is 

 another characteristic of this order. 



FAMILY ANOMIID.K 

 GENUS Anomia 



This is a family of peculiar and highly specialized forms. 

 Anomia has an irregularly rounded shell, with one convex and 

 one flat or concave valve. There is no regular hinge or well- 

 defined hinge-margin, but a raised fossette, or cartilage plate, occu- 

 pies a position at the top of the valves. In the flat valve there 

 is a large oblong hole just under the apex, through which projects a 

 calcified byssus, by means of which the animal secures itself to 

 oysters, dead shells, stones, or any solid object. The anomias, which 

 have become stationary in habit, have practically lost their foot. 

 The gills are very large and curved, while all the organs seem to 

 be abnormally placed on account of the huge byssus and byssal 

 muscle. For the byssus to pass, as it does, through a specially 

 prepared hole in one of the valves is an extraordinary departure 

 from the conventional types of byssiferous species. The heart is 

 not traversed by the intestine. Altogether, then, Anomia is a very 

 curious genus. 



A. simplex. The commoner large form of New England. It varies 

 from one to three inches in diameter, is exceedingly irregular in shape, 



and its surface is var- 

 iously undulated and 

 plaited in accordance with 

 the surface of the ob- 

 ject to which it is at- 

 tached. Thousands of 

 these valves, disjointed 

 and separated, are cast 

 upon the beaches all along 

 our Atlantic coast. They 

 are light green to sal- 

 mon- or copper-color, 

 generally fragile and 

 scaly, and have a pecu- 

 liarly dulled (as though 



Anomia simplex, side view. Anomia simplex, from below. greased) nacre. 



