FAUNA. The indigenous animals of a desig nated place, region, or space of time, considered collectively—the correlative of 'flora' (q.v.). The space in view may he a geographical surface, as a country, or a certain neighborhood; or it may be a certain environment. Moreover, the word is frequently compounded. as `avifauna.' pisei fauna,' etc., in order to designate that only the birds, fishes, or other single group of the given region are under consideration. Conversely, a district characterized by a fauna of any par ticular nature is spoken of as a 'faunal region.' For further elucidation of these definitions, see DISTRIBUTION OF' ANIMALS.
In geology and paleontology, the term is em ployed in a sense somewhat different from that in which it is used by the zoologist. The pale ontologist conceives of a 'fauna' as an assemblage of animals inhabiting a particular region during a geologic hemera, epoch, or period. The fossil
remains of such a fauna would he found scattered through the successive layers of all the deposits formed during the period of its existence. Such a fossil fauna undergoes changes in its make-up; some species drop out, other new ones come in from adjoining provinces, and the species them selves often exhibit evolutional changes. The broader the use of the term, the more apparent the modifications of the fauna. Thus the 'Ordo vician fauna' of New York State is a compre hensive use of the term, and involves a large, heterogeneous assemblage of fossil organisms; but the 'Upper Chazy' fauna of the Champlain Valley is a more restricted use and refers to a concrete, homogeneous member of the larger group. For further discussion, see PALEONTOLOGY.