Calyptrea

Calyptrea, a genus of molluscs, among Prosobranch Gastropods, and sometimes popularly known as Chambered, Cup and Saucer, Bonnet, or Slipper Limpets. The shell is indeed more or less limpet-like, but that ends the resemblance, while even in regard to the shell, the presence of a slight spiral, and of an intrenched internal plate for the attachment of the principal muscle, are quite sufficiently distinctive. The shapes vary considerably. Some ten living species are known, mostly from warmer waters, though two are recorded as British. From the chalk deposits, however, three times as many species are known. The name Patella, or Limpet, was formerly mistakenly used to include Calyptrea and allied genera like Galerus and Crepidula. Pileopsis (hungarica), the Hungarian Cap Shell, is allied, and occurs in the Atlantic and Mediterranean.