Trochidae ID help

[paul monfils]

I believe this is Omphalius nigerrimus, a member of a rather confusing group of Trochidae. They are closely related to Tegula and Chlorostoma species, and in older books you sometimes see them all lumped together under Tegula. Also you may see this species listed as Chlorostoma nigerrima. It's a confusing group because quite a few species are similar to one another, and some of them are also quite variable within a species. However, only a few species have the vertical ribbing on the whorls like this one.