Var pellucidus. 



MODIOLA. 185 



well as in the thin ones ; and, on the other hand, the thin ones are 

 often without radiations. Turton thinks it may always be distin- 

 guished " by having only two or three tubercular teeth under the 

 beaks." But this does not accord with my observations. 



The shell is subject to many distortions from accident, and from 

 the form of the bodies on which it grows, or of cavities in which it 

 becomes wedged. Hence, probably, arises that curved form which 

 takes the name of M. incurvatus. 



This mussel is one of the most common and best known of all 

 our shells. It is very extensively 

 distributed throughout all north- 

 ern seas. It is abundant on the 

 coasts of England, France, Nor- 

 way, and Russia, where it is ex- 

 tensively used as food, as its name 

 imports, and also for manure. 

 In this country it has, as yet, 

 been put to no economical use, 

 though I am assured by a friend of acknowledged good taste, that 

 when cooked it is more palatable than the common clam. Unlike 

 the Modiola modiolus, it appears to inhabit shallow waters, in posi- 

 tions where it is left uncovered at the recess of the tide. It attaches 

 itself by its byssus to rocks and timbers, and may be thus seen under 

 bridges and other submerged structures, in shallow inlets with a 

 pebbly Ijottom, and especially on rocks not far from high-water 

 mark, clinging in immense crowds of all sizes, colors, and figures ; 

 some beautifully radiated, some dark blue-black, and others light 

 horn-color ; some beautifully smooth, regular, and glistening, others 

 distorted, rough, and dingy ; the whole surface of tlie young shell 

 is beset with a bristly beard. While, like the Modiola plicatula, 

 it clusters about the shore, it does not, like that, bury itself in the 

 mud, but is always exposed and attached to some solid body. It is 

 common to find it wedged in among the rocks and crevices of such 

 shores as Nahant and Cape Ann. 



Eastport, common ( Cooper) : Nova Scotia ( Willis) ; James Bay 

 {Drexhr^ ; Goodhaven (^Hai/es) ; fossil in the valley of the St. 

 Lawrence. 



Genus MODIOLA, Lamarck. 1790. 



Shell oblique, wedge-shaped ; beaks very near the anterior end ; 

 hinge as in Mytiliis ; impression of the mantle irregular. 



