possibly arise, whether the tartareous scales really belong
to i t ; but the best examination we can give leads us to believe
they do. The tubercles have a black shell, apparently
single, and a brownish grey nucleus. Their body is oval, and
a cylindrical neck rises either through or between the scales
of the crust. In the latter situation they sometimes form
crowded lines, the exposed portion is rarely polished, sometimes
conical with a central impression, sometimes truncate
with an open pore, which occasionally becomes irregular.
We are not acquainted with V. spongiosa of Acharius ;
but, from the description and figure, it must differ widely
from the present species. g_
