Fig. 56.—Terebratula sacculus (Martin). Carboniferous.
Fig. 57.—Brachiopods; genus Orthis.
a, O. Billingsi (Hartt). Lower Cambrian. b, O. pectinella (Hall). Siluro-Cambrian. c, O. lynx (Eichwald). Siluro-Cambrian.
Fig. 58.—Rhynchonella increbrescens (Hall). Siluro-Cambrian.