Biologic evolution

It is feeling that keeps writing the interest of corbicula's shell.
It had written before.
At present, the answer is not understood after all.
Putting the camera in the river and taking a picture of the quickest are the
most convincing, and it doesn't exist in ..explanation.. necessity.
However,
It is considerably difficult for me of the amateur to go to the river where
the corbicula is taken, and to see the fisherman's work.
The place is not understood because it goes by ship though even I can go if
it is a nearby river.
Moreover, it thought about the reason by arranging it.



Because the stone and the tree, etc. in the apex of shell knock
against, the possibility of damaging it thinks it is high the shell
this figure.
In addition,
Because the standing position in littleneck clam's sand is also the
same, it is thought it is more realistic.