Trias. The name given on the continent to the beds of the New red sandstone series.
Trilobite. A common fossil in the Dudley limestone, so named from the characteristic species having the body divided into three lobes. Trilobites are the remains of a remarkable extinct family of Crustaceans, of which the crab, lobster, &c., are modern representatives.
Trionyx. A genus of tortoise, having three claws.
Tufaceous, Tuff. An Italian name for a variety of volcanic rock of earthy texture, and made up chiefly or entirely of fragments of volcanic ashes.
Turbinated. Shells which have a spiral or screw-like structure are thus named.
Unconformable superposition (instratification). The condition of strata when one has been deposited horizontally upon the upturned edges of those immediately below.
Unio. Fresh water bivalve.
Vertebrata, or Vertebrated Animals. A large and most important division of the animal kingdom, including all those animals provided with a back bone. Each separate bone of the back is called a vertebra.
Vertex. The summit or upper part of a solid.
Vitreous. Glassy. Used in Mineralogy to designate a peculiar luster.