Search the Dictionary

The Silurian age.

The earliest period in geological period, extending up to the Lower Silurian. It includes an Azoic age, previous to the appearance of life, and an Eozoic age, including the earliest forms of life.

A genus of trilobites found in the Lower Silurian formation. See Illust. in Append.

A extinct genus of Branchiopoda, very common in Silurian limestones.

alcite, or carbonate of lime. Calciferouse epoch (Geol.), and epoch in the American lower Silurian system, immediately succeeding the Cambrian period. The name alludes to the peculiar mixture of calcareous and siliceous characteristics in many of the beds. See the Diagram under Grology.

A genus of trilobites characteristic of the Silurian age.

Of or pertaining to the lowest subdivision of the rocks of the Silurian or Molluscan age; -- sometimes described as inferior to the Silurian. It is named from its development in Cambria or Wales. See the Diagram under Geology.

ive or inhabitant of Canada. Canadian period (Geol.), A subdivision of the American Lower Silurian system embracing the calciferous, Quebec, and Chazy epochs. This period immediately follows the primordial or Cambrian period, and is by many geologists regarded as the beginning of the Silurian age, See the Diagram, unde…

A genus of fossil corals, common in the lower Silurian limestones.

hain coral (Zoöl.), a fossil coral of the genus Halysites, common in the middle and upper Silurian rocks. The tubular corallites are united side by side in groups, looking in an end view like links of a chain. When perfect, the calicles show twelve septa. -- Chain coupling. (a) A shackle for uniting lengths of chain,…

An epoch at the close of the Canadian period of the American Lower Silurian system; -- so named from a township in Clinton Co., New York. See the Diagram under Geology.

An epoch at the close of the American lower Silurian system. The rocks are well developed near Cincinnati, Ohio. The group includes the Hudson River and Lorraine shales of New york.

rivers and valleys, formerly supposed to be of one formation, but now known to be partly Silurian and partly Devonian.

n system (Geol.), the slate or graywacke system of rocks, now included in the Cambrian or Silurian system; -- so called because most prominent at Cumberland.

A genus of trilobites, of many species, common in the Upper Silurian and Devonian rocks.

A name formerly given to certain Silurian brachiopod shells of the genus Spirifer. Delthyris limestone (Geol.), one of the divisions of the Upper Silurian rocks in New York.

ystem. Devonian age (Geol.), the age next older than the Carboniferous and later than the Silurian; -- called also the Age of fishes. The various strata of this age compose the Devonian formation or system, and include the old red sandstone of Great Britain. They contain, besides plants and numerous invertebrates, the…

A fossil plant which is found in the lowest beds of the Silurian age.

A genus of extinct Merostomata, found in Silurian rocks. Some of the species are more than three feet long.

A genus of fossil corals abundant in the Silurian and Devonian rocks, having polygonal cells with perforated walls.