84 BULLETIN OF THE NATURAL HISTORY SOCIETY. 
17. Margaritana arcuata (Barnes) Stimpson. 
[The fresh-water 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 Margaritana 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 pearl; arcuata , 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.) Rivers in Annapolis, Sackville 
River, 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 
