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Paleozoic era

(Encyclopedia) Paleozoic era pā˝lēəzō´ĭk, a major division (era) of geologic time (see Geologic Timescale, table) occurring between 570 to 240 million years ago. It is subdivided into six periods,…

Siberian Platform

(Encyclopedia) Siberian Platform or Angara Shield, large, geologically stable area of Precambrian rocks, N Asia, comprising much of Siberia, Russia. It is bounded, in general, on the west by the…

Logan, Sir William Edmond

(Encyclopedia) Logan, Sir William Edmond, 1798–1875, Canadian geologist. Educated in England, he managed (1831–38) coal mines and a copper smelter in Wales. In addition to making studies of clays…

Triassic period

(Encyclopedia) Triassic period trīăs´ĭk, first period of the Mesozoic era of geologic time (see Geologic Timescale, table) from 205 to 250 million years ago. Throughout the Triassic, E North America…

Permian period

(Encyclopedia) Permian period pûr´mēən [from Perm, Russia], sixth and last period of the Paleozoic era (see Geologic Timescale, table) from 250 to 290 million years ago. Historical Geology of the…

Phoronida

(Encyclopedia) Phoronida fərŏn´ədə, small phylum of slender, wormlike marine tube-dwellers, typically found in temperate, shallow seas. About 10 species are known. Although the body is free in the…

White Mountains

(Encyclopedia) White Mountains, part of the Appalachian system, N N.H. and SW Maine, rising to 6,288 ft (1,917 m) at Mt. Washington in the Presidential Range and to 5,249 ft (1,600 m) at Mt.…

trilobite

(Encyclopedia) trilobite trī´ləbīt˝, subphylum of the phylum Arthropoda that includes a large group of extinct marine animals that were abundant in the Paleozoic era. They represent more than half of…

Carboniferous period

(Encyclopedia) Carboniferous period kärbənĭf´ərəs, fifth period of the Paleozoic era of geologic time (see Geologic Timescale, table), from 350 to 290 million years ago. Historical Geology of the…

cephalopod

(Encyclopedia) cephalopod sĕf´ələpŏd˝, member of the class Cephalopoda, the most highly organized group of mollusks (phylum Mollusca), and including the squids, octopuses, cuttlefish, and nautiluses…