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An extinct order of amphibians found fossil in the Mesozoic rocks; called also Stegocephali, and Labyrinthodonta.

m the solid state without apparent melting; -- said of those substances, like arsenic, benzoic acid, etc., which do not exhibit a liquid form on heating, except under increased pressure.

Any one of numerous species of small, conical fossil shells found in Paleozoic rocks. They are supposed to be pteropods.

t. -- Tertiary period. (Geol.) (a) The first period of the age of mammals, or of the Cenozoic era. (b) The rock formation of that period; -- called also Tertiary formation. See the Chart of Geology. -- Tertiary syphilis (Med.), the third and last stage of syphilis, in which it invades the bones and internal organs.…

to, or derived from, thiophene; specifically, designating a certain acid analogous to benzoic acid.

of three metameric acids, CH3.C6H4.CO2H, which are related to toluene and analogous to benzoic acids. They are white crystalline substances, and are called respectively orthotoluic acid, metatoluic acid, and paratoluic acid.

of pearly bivalve shells, numerous extinct species of which are characteristic of the Mesozoic rocks. A few living species exist on the coast of Australia.

common in the Silurian and Devonian periods, but became extinct at the close of the Paleozoic. So named from the three lobes usually seen on each segment.

ally, it consists of oxyphenol and amidopropionic acid, and by decomposition yields oxybenzoic acid, or some other benzol derivative. [Written also tyrosine.]

An extinct genus of cyathophylloid corals common in the Paleozoic formations. It is cup-shaped with numerous septa, and with a deep pit in one side of the cup.