174 'THIRTY-FIFTH REPORT ON THE STATE MUSEUM. 
kept for ten months has gained in length in that time only one-fourth 
of an inch, but it seems probable that their growth in their natural 
habitat must be much greater than this. 
In a certain locality in a stream near Albany, Unio pressus is quite 
abundant in a rapid portion, about two hundred feet in length. 
I have collected all the large specimens each year for three years. The 
water being so shallow that every portion of the bottom can be seen, 
and yet each year they appear equally abundant and of full size, show- 
ing that their growth must be quite rapid. 
When out of water, and exposed to the sun, the Anodonta will live 
but a short time; placed in a cool, somewhat damp situation, life will 
continue for several days. Other members of the family Unionide are 
much more tenacious of life. According to DESHAYEs, de Conch, pp. 
81-84, a specimen of Anodonta from Cochin China reached Paris in 
a living condition after having been wrapped in dry paper for a period 
of more than eight months; similar instances are mentioned concerning 
Unio litoralis (Drap.), Spatha rubens (Lam.) and an Australian species 
of Unio, the last surviving two hundred and thirty-one days. None of 
those with which I have experimented have survived more than seven 
days, and the greater portion of them died within two or three days. 
The popular belief that the removal of a bivalve from the shell is 
instantly fatal to the animal is erroneous. While making the draw- 
ings illustrating this article, I cut through the muscles attached to one 
of the valves, removing the valve; and, after some hours occupied in 
making the drawing (Pl. 5), I removed the animal entirely from the 
shell, cutting away the mantle from one side, and spent about an hour 
in noting the action of the ventricle and auricles. The action of the 
heart at this time, eight hours after the valve was removed, was full 
and regular. 
The heart continues its action for a considerable time after all appar- 
ent muscular force has been lost. I once noticed in the tank one of 
the Anodonte, to all appearances dead, the shell gaping, the foot pro- 
truding, no contraction occurring on handling, and no evidence of life 
apparent. Not having time to dissect it that day, I laid it away in 
cold water ; about twenty-four hours afterward Iremoved the animal 
from the shell, not the slightest contraction occurring, and yet the 
heart was distinctly beating, though slowly. 
THE MANTLE. 
(Plate 6.) 
If a shell be opened by inserting a knife between the valves and 
cutting, close to the shell, the anterior and posterior muscles, a thin, 
semi-transparent membrane will be observed completely investing the 
