They are generally of small size.
EOCENE .-- The earliest of the three divisions of the Tertiary epoch of geologists.

Rocks of this age contain a small proportion of shells identical with species now living.
EPHEMEROUS INSECTS .-- Insects allied to the May-fly.
FAUNA .-- The totality of the animals naturally inhabiting a certain country or region, or which have lived during a given geological period.
FELIDAE .-- The Cat-family.
FERAL .-- Having become wild from a state of cultivation or domestication.
FLORA .-- The totality of the plants growing naturally in a country, or during a given geological period.
FLORETS .-- Flowers imperfectly developed in some respects, and collected into a dense spike or head, as in the Grasses, the Dandelion, etc.
FOETAL .-- Of or belonging to the foetus, or embryo in course of development.
FORAMINIFERA .-- A class of animals of very low organisation and generally of small size, having a jelly-like body, from the surface of which delicate filaments can be given off and retracted for the prehension of external objects, and having a calcareous or sandy shell, usually divided into chambers and perforated with small apertures.
FOSSILIFEROUS .-- Containing fossils.
FOSSORIAL .-- Having a faculty of digging.

The Fossorial Hymenoptera are a group of Wasp-like Insects, which burrow in sandy soil to make nests for their young.
FRENUM (pl.FRENA) .-- A small band or fold of skin.
FUNGI (sing.

FUNGUS) .-- A class of cellular plants, of which Mushrooms, Toadstools, and Moulds, are familiar examples.
FURCULA .-- The forked bone formed by the union of the collar-bones in many birds, such as the common Fowl.
GALLINACEOUS BIRDS .-- An order of birds of which the common Fowl, Turkey, and Pheasant, are well-known examples.
GALLUS .-- The genus of birds which includes the common Fowl.
GANGLION .-- A swelling or knot from which nerves are given off as from a centre.
GANOID FISHES .-- Fishes covered with peculiar enamelled bony scales.

Most of them are extinct.
GERMINAL VESICLE .-- A minute vesicle in the eggs of animals, from which the development of the embryo proceeds.
GLACIAL PERIOD .-- A period of great cold and of enormous extension of ice upon the surface of the earth.