The Elements of Geology

by William Harmon Norton

Fig. 283. A Bryozoan

Bryozoans. No fossils are more common in the limestones of the time than the small branching stems and lacelike mats of the bryozoans,—the skeletons of colonies of a minute animal allied in structure to the brachiopod.

Fig. 284. Ordovician Brachiopods

Fig. 285. A, Cyrtoceras; B, Trochoceras; C, Lituites

Brachiopods. These multiplied greatly, and in places their shells formed thick beds of coquina. They still greatly surpassed the mollusks in numbers.