PHOLIS, in natural history, is the name of a genus of fossils of the class of gypsums or plaster-stones. Its distinguishing characters are, that the bodies of it are tolerably hard, composed of particles somewhat broad, and of a bright crystalline lustre. The name is derived from pholis, a scale or small flake, because they are composed of particles of that form.
The species of this genus are very valuable, and perhaps the most so of all the gypsums, because they burn to the best and finest plaster, but so far as is yet known, there are but two of them: the fine plaster-stone of Montmartre in France, called by us plaster of Paris stone and parge; and the other, the coarser and somewhat reddish kind, common in many parts of England, and called hall plaster. See PLASTER of Paris.