84 THK ECONOMIC MOLLUSC A OF ACADIA. 



17. Margaritana arciiata (Barnes) Stimpson. 



[The fresb-vvater Mussels of Acadia have not been 

 well studied. Willis and Jones mention several species 

 as occurring in Nova Scotia; Mr. G. F. Matthew knows 

 of several in New Brunswick; and Dr. Dawson has 

 reported two species from Prince Edward Island. It 

 is uncertain how many of these may produce pearls, 

 perhaps all of them under the requisite conditions. 

 Mr. Matthew tells the writer that Mr. S. E. Gerow has 

 identified 3Iargaritana arcuata in the Society's collec- 

 tion, as the pearl-bearing species of our waters.] 



Fresh-water Mussel, Fresh-water Clam, Pearl-Mussel. 



■ Mic-mac, Sebooaas-uk. 



{Margaritana, a, ■pea.v\\ ftccuafrt, arched]. 



Distribution, (a) General; — Fresh-water streams of 

 North-eastern America. 



(h) In Acadia; — (in N. B.) Streams of southern counties, 

 8. E. Gerow. (In N. S.) Elvers in Annapolis, Sackville 

 Eiver, Willis. All fresh- water streams, Jones. Not reported 

 from Prince Edward Island. 



Habits. Our fresh-water Mussels are in general not unlike their 

 salt-water namesakes in appearance and habits. The epidermis or outer 

 skin varies from straw-color to olive-green, and is not attractive, but 

 within the shells nearly always show the beautiful changing colors of 

 mother-of-pearl. 



They generally lie partly buried at the bottom of the pond or 

 stream in which they live, with the posterior end protruding and 

 gaping open. But by means of their powerful " foot," they can travel 

 with some facility, and one often sees on sandy bottoms the long 

 furrows left by them in their progress. The young are kept for a time 

 in the gills of the parent. Our eastern species present little variety as 

 to shape, size and color, but those of the west show the most remarkable 

 diversity in these respects. 



Pearls are, for the most part, found only in old or deformed shells. 

 Mr. Gerow says that young or even middle-aged specimens very rarely 

 or never contain them. They are believed to be formed only as the 

 result of some disease, injury or irritation to the animal. Some 

 naturalists have thought that the free perfect pearls are formed by the 



