PEARLY FRESH-WATER MUSSELS OF THE UNITED STATES. 
283 
and ascend a near-by stream, carrying with them the encysted mussels, which might 
be dropped in the second stream entered. Of course, when thus inclosed in the pro- 
tecting cyst they could be carried through the sea without injury. 
The pearly mussels live in a great variety of conditions. Most of them are found 
in shallow water, but certain forms live at considerable depths. Arnould Locard is 
authority for the statement that Unio prosacrus lives down to 50, 100, or even 200 metres 
in Lake Tiberias.* Others live at great depths in the African Lake Tanganyika. In 
Florida I have seen myriads of Ihiio tortivus buried among the fibrous roots of trees, 
and in the muddy, sandy banks just below the surface of the water, LmnpsiUs ano- 
dontoides of our western rivers sometimes burrows to the depth of a foot or more, and 
the curious Anodonta anfiulata of California and Oregon buries itself in hard clay in 
rapid water, with the wide posterior end down stream, allowing the sharp angle along 
this part of the shell to just come to the surface of the clay, so that it presents little 
resistance to the current. Our curious Margaritana dehiscens has a greatly elongated 
foot, and burrows deeply in the mud at the bottom of the streams, and the same is true 
of the South American Mycetopoda and the 
Chinese Solenaia. These forms probably do 
not migrate under any ordinary circum- 
stances. I have reason to believe that the 
species which plow furrows on the bottoms 
of ponds and streams often migrate. 
Ordinarily, the pearly fresh-water mus- 
sels die in a short time if taken out of the 
water — in 24 to 48 hours, as a rule. I have 
had thousands of specimens taken alive, 
packed tightly in boxes, and sent to me at 
Washington by mail or express from various 
parts of the country, from as far as Texas, 
Dakota, Florida, or- Maine. Perhaps half of 
these reached me in a living condition when 
they came through promptly. Generally 
they die when exjrosed a few hours in the sun. Once when collecting in Indian 
Territory I came upon an artificial pond at McAlester which had been drained only 
a few days, and all over the soft bottom the water stood in puddles. Thousands of 
TJnio suhrostratus and tetralasmus were lying dead in the mud, and the odor was so 
sickening that I could scarcely collect them. Yet, under certain circumstances, both 
species will live buried in dried mud for a long time. Hon. J. 1). Mitchell, of Victoria, 
Tex., kept specimens of tetralasmus alive in a dry room for many months. 
In June, 1850, a living pond mussel was sent to Mr. Gray in London, from 
Australia, which had been out of water more than a year.t In a small stream near 
Braidentown, Fla., a great colony of Vnio obesus is established. This stream or 
drain is in the piney woods, and only runs during some three months in the summer — 
the rainy season. The rest of the year it is dry, and thousands of these mussels may 
be found just buried in the sandy banks, or among the flags and rushes of the bottom 
where there is very little moistui-e; yet all are healthy. I have laid these mussels 
out in the sun for months, after which nearly all of them were found to be alive. 
There can be but little doubt that the specimens which live in perennial water soon 
K.i. b. — Qiiadrula e6cnaLe.i. Niggerliead of tho button 
inanufocturers. Toung shell tiiteii in its tenth year. 
This has young in all four leaves of the brauchiie. 
'Arch. d’Hist. Nat. tie Lyon, 1883, p. 
t Wootlward’s Manual of the Mollusca, 18.51), p. 18. 
