Having the two sides unlike.

ATROPHIED.--Arrested in development at a very early stage.

BALANUS.--The genus including the common Acorn-shells which live in
abundance on the rocks of the sea-coast.

BATRACHIANS.--A class of animals allied to the Reptiles, but undergoing
a peculiar 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.--A series of very ancient Palaeozoic rocks, between the
Laurentian and the Silurian. Until recently these were regarded as the
oldest fossiliferous rocks.

CANIDAE.--The Dog-family, including the Dog, Wolf, Fox, Jackal, etc.

CARAPACE.--The shell enveloping the anterior part of the body in
Crustaceans generally; applied also to the hard shelly pieces of the
Cirripedes.

CARBONIFEROUS.--This term is applied to the great formation which
includes, among other rocks, the coal-measures. It belongs to the
oldest, or Palaeozoic, system of formations.

CAUDAL.--Of or belonging to the tail.

CEPHALOPODS.--The highest class of the Mollusca, or soft-bodied animals,
characterised by having the mouth surrounded by a greater or less
number of fleshy arms or tentacles, which, in most living species, are
furnished with sucking-cups. (Examples, Cuttle-fish, Nautilus.)

CETACEA.--An order of Mammalia, including the Whales, Dolphins, etc.,
having the form of the body fish-like, the skin naked, and only the fore
limbs developed.

CHELONIA.--An order of Reptiles including the Turtles, Tortoises, etc.

CIRRIPEDES.--An order of Crustaceans including the Barnacles and
Acorn-shells. Their young resemble those of many other Crustaceans in
form; but when mature they are always attached to other objects, either
directly or by means of a stalk, and their bodies are enclosed by a
calcareous shell composed of several pieces, two of which can open to
give issue to a bunch of curled, jointed tentacles, which represent the
limbs.

COCCUS.--The genus of Insec