trimerella

from The Century Dictionary.

• noun A genus of atrematous brachiopods having thick calcareous biconvex shells of ovate outline, with prominent cardinal areas. The interiors of the valves are provided with long, narrow, doubly vaulted platforms extending forward from the hinge-plates. The genus is represented in the Upper Silurian dolomites of the Baltic region of Europe and in the Guelph dolomites of similar age in North America.