The Mesozoic Mammalia

Abstract

IN the elaborate memoir before us, comprising eighty quarto pages of text, illustrated by thirty woodcuts and two plates, Prof. Osborn, of Princeton College, New Jersey, gives us the result of his researches into the structure of the Mesozoic and allied Tertiary Mammals, based upon observations carried on both in America and Europe. As a rule, these Mammals are of small size, and are mainly known to us by more or less imperfect jaws and teeth; by far the greater number of specimens consisting of the lower jaw or mandible. Now, it is well known that even in groups of the smaller Mammals which are well represented at the present day, such as the Shrews among the Insectivora, or the Bats, it is almost, if not quite, impossible to recognize many of the genera, to say nothing of the species, when we have to deal only with a series of fossil or sub-fossil lower jaws from the cavern or later Tertiary deposits. And if this be so in groups with which we are well acquainted, the difficulty is of course increased many times over when we have to deal with forms having no close analogues among the existing fauna. The puzzle is further increased by the difficulty of referring such portions of upper jaws as are more rarely found to the species indicated by mandibles; and this induces a great danger of founding species or higher groups upon the evidence of upper jaws, which cannot be decisively shown to be distinct from those founded upon the evidence of the mandibles. Prof. Osborn, as will be noticed below, has not altogether steered clear of this danger; and we consider it would be advisable in delicate researches of this nature to lay down a rule that family or higher groups should only be formed upon the evidence of homologous parts, even if genera and species have been named upon the evidence of dissimilar parts of the skeleton.

The Structure and Classification of the Mesozoic Mammalia.

By H. F. Osborn. Journ. Ac. Nat. Sci. Philadelphia, Vol. IX. No. 2. (Philadelphia: Published by the Academy, 1888.)