PALEONTOLOGY. The study of the life which inhabited the earth during past geological periods. It is based on the study of fossils. Although it was long recognized that fossils were the re mains of past life, and some attempt at study has been made, paleontology was placed on a scientific basis by Culver (1769-1832) and given great impetus by the publication of Darwin's "Origin of Species" in 1859, which presented the theory of evolution which was de pendent upon the paleontologist for its proof.
There are two branches of paleontol ogy—the branch of the science which studies the biological features of the fos sils, and the more comprehensive geo logical branch which studies the rela tions between the fossils and the rocks and determines their period by them. Needless to say, the science is closely re lated to physical geography as well as biology and geology.
A very large portion of the life of for mer geological periods has not been pre served for us in the form of fossils, either because it was not of such a type as would lend itself to fossilization, or the evidences of the fossilization have been destroyed by erosion or the meta morphosis of the rocks in which they were imbedded, but in spite of these many gaps the history of organic development is rapidly being compiled and the ad vance of various types of life through successive geological periods has been studied.
Of course the animal and vegetable life inhabiting the earth at the time a rock is formed will be the fossils which are found in that rock, and evidence of the predominance of different types of life in various geological periods and the sequence of these periods has been de termined. The major geological periods
or eras take their names from the type of life predominating, and the divisions of these periods are named from the spe cies. During the Paleozoic era the earth was inhabited by invertebrates, by rep tiles during the Mesozoic era and by mammals in the Cenozoic era.
The fauna which are found in the lowest strata are those which originally were best adapted to the locality and which had conquered in the struggle for existence. These are indigenous faunas. Often the changes in the climate or topog raphy of the locality cause the intro duction of a new type of life called ex otic fauna, which may either die out, or thrive and become the predominating or indigenous fauna of the locality.
Bionomy is that branch of paleontolo gy which deals with marine organisms and its branches are: Plankton, which considers those forms of life which drift with the current; Nekton, the study of the swimming types; and Benthos, the life of the bottom of the ocean. The de posits found at beaches and in shallow places are called Littoral Facies; those in moderately deep water Sub-littoral Facies, and the deposits of the deep sea are Abyssal Facies.
The study of the ranges of tempera ture and the temperature zones of geo logical time, the discovery of extinct spe cies and even orders, the proof of changes in type in adaptation to circumstances have been some of the results of paleon tological research.