the Shells of Maine. 311 



fixtures of every sort, on the whole line of coast, east and 

 west. 



B. elongaius, Lin. This is found in company with the 

 preceding species, and is also very plenty. It is probably 

 a mere variety of it, as they are often grouped together in 

 such a manner and in such imperceptible gradation that it is 

 impossible to determine where one species begins or the other 

 ends. It is most abundant, and attains the greatest perfec- 

 tion, in still water, and seated upon wooden fixtures. 



B. tintinnabulum, Lin. Lam. I found four or five stinted 

 specimens of this species, near fort Preble, situated in a deep 

 excavation in a ledge, near low-water mark, covered by ma- 

 rine plants, in which situation they were always under water. 



Genus Anatifa. Lam. 



A. lavis, Lin. This species is occasionally found in some 

 of the old docks in Portland harbor, fixed to sunken timbers. 



A. striata, Lin. Bruguiere. This is found in company 

 with the preceding. 



A. dentata, Wood. This is always found in company with 

 the two preceding species, but is much less abundant than 

 either. The three species are found in the greatest profusion 

 on the bottoms of vessels, arriving from the West Indies. I 

 have no doubt I have seen twenty bushels of them on the 

 bottom of a single vessel. Neither of the above species can 

 be, properly, regarded as indigenous to this State, but they 

 have all, probably, been imported from the south, and without 

 fresh importations, none of them would be maintained through 

 many generations. 



There is much good reason for doubting the propriety of sep- 

 arating the above into distinct species. We often find them 

 all grouped together within the space of a square inch, and I 

 have frequently found each of them adhering to the pedicles of 

 the others ; and as to the form of the valves, the color of the 

 pedicles, d:c. these are constantly varying and interchanging, 

 so that they afford no certain data on wiiich to establish spe- 

 cific distinctions. 



