Graptolites or Sea-Pens. Fossils of the lower Silurian system.
Grauwacke or Graywacke. The name given by German geologists to some of the older fossiliferous rocks, and generally of a gray color, sandy composition, and fissile nature.
Gryphiæ. Fossil bivalve shells found in the Lias, &c.
Habitat. The natural district to which a species of animals or vegetables is confined in its distribution.
Hexahedral. Having six equal sides.
Heterocercal. Applied to the tail of a fish, means that the upper lobe extends farther than the under.
Heteropoda. An order of univalve molluscs, whose feet form a kind of fin.
Holoptychius. A Ganoid fish of the coal-measures.
Hornblende. An important mineral in the composition of some rocks.
Homocercal. Applied to fishes having equal lobed tails.