Hornstone. A variety of quartz found in volcanic districts.
Hyaline. Transparent like glass.
Hybodentes. Fossil fish.
Hylæosaurus. Fossil lizard of the Wealden.
Hypersthene. A mineral.
Hypogene Rocks. Rocks formed beneath others or which are assumed to have obtained their present aspect underneath the earth’s surface.
Ichthyodorulite. The fossil spine of certain fishes resembling sharks.
Ichthyolites. Fragments of the bones of fossil fishes.
Ichthyology. The study and description of fishes.
Ichthyosaurus. A marine reptile (fish-lizard), whose remains are very abundant in rocks of the Secondary period.