Terebratula

Terebratula, one of the best known genera of "Lamp-shells" or Brachiopoda, the type of the family Terebratulidae. The animal has a bivalve shell, with one valve much larger than the other, and provided with a beak perforated by a pore through which passes the "peduncle," that fixes the animal to some support. The shell is smooth, except that it may have one or more broad folds on the margin, and is never marked by ribs as in the Terebratella. The support for the gills is short; those forms in which it is long are now separated as the genus Magellania (better known as Waldheimia), many of the species of which cannot be distinguished from Terebratula by external characters. As now limited, the genus ranges from the Devonian to the present time; it is most abundant in the Jurassic and Cretaceous periods.