Peniculauris bassi belongs to the family Productidae, so we call it a “productid” brachiopod. The name Peniculaurisis the genus of the animal, and Peniculauris bassi indicates the species. Since only various parts protrude from the rocks, it is difficult to form a mental picture of the shell. Here is a cross section of this large, robust shell. Another productid genus, Rugatia, is also common here. Rugatia is usually smaller and more strongly bi-lobed than Peniculauris.