metamorphosis, in which the young animal is generally aquatic and breathes by gills.

(Examples, Frogs, Toads, and Newts.)

BOULDERS. — Large transported blocks of stone generally embedded in clays or gravels.

BRACHIOPODA. — A class of marine Mollusca, or soft-bodied animals, furnished with a bivalve shell, attached to submarine objects by a stalk which passes through an aperture in one of the valves, and furnished with fringed arms, by the action of which food is carried to the mouth.

BRANCHIAE. — Gills or organs for respiration in water.

BRANCHIAL. — Pertaining to gills or branchiae.

CAMBRIAN SYSTEM.