Echinodermata [Gr.,=spiny skin], phylum of exclusively marine bottom-dwelling invertebrates having external skeletons of calcareous plates just beneath the skin. The plates may be solidly fuse...

Driesch, Hans Adolf Eduard, 1867–1941, German philosopher, b. Bad Kreuznach, grad. (zoology) Univ. of Jena, 1889. His early interest in biology was gradually overshadowed by involvement in phi...

Hydrothermal vent, crack along a rift or ridge in the deep ocean floor that spews out water heated to high temperatures by the magma under the earth's crust. Some vents are in areas of seafloo...

Carboniferous period, fifth period of the Paleozoic era of geologic time (see Geologic Timescale, table), from 350 to 290 million years ago. The Carboniferous period was marked by vast, coal-f...

Sand dollar, common name for a marine animal in the same phylum as the starfish (see sea star). The sand dollar has a rigid, flattened, disk-shaped test, or shell, made of firmly united plates...

Cretaceous period, third and last period of the Mesozoic era of geologic time (see Geologic Timescale, table), lasting from approximately 144 to 65 million years ago. The Cretaceous was marked...

Flatfish, common name for any member of the unique and widespread order Pleuronectiformes containing over 500 species (including the flounder, halibut, plaice, sole, and turbot), 130 of which ...