The shell was slightly concave, the concavity turned to the front.
And otherwise unlike a volcanic crater is the concavity itself.
It is circular, and is placed on the concavity of the ventral flexure.
Petals numerous, small, 1-lipped, the concavity near the base.
Three, however, had had their concavity partly whittled flat.
The Bee seems to make a point of this concavity, ...