Some Extinct Vertebrate Animals from North America 1

Abstract

A NEW volume of collected papers, published by the American Museum of Natural History, New York, enables us to realise how important and numerous are the additions to our knowledge of extinct vertebrate animals still made by systematic explorations in North America. The contributions now received deal with the work of only four years, 1904–8, accomplished by one institution; but they make great advances in nearly all parts of the subject to which they relate, and their value is increased by the excellent text-figures and plates with which they are illustrated. The pioneer discoveries of Leidy, Marsh, and Cope furnished; for many years a continual series of surprises for the student of extinct vertebrates; their successors during the past decade and a half have not only filled in many details in the preliminary view thus obtained, but have also been scarcely less successful in recovering unexpected groups and missing links. Present explorers have, indeed, the advantage of being able to pursue their work in the remote west in peaceful leisure, without any armed escort, and so have facilities for determining the relative positions of the strata from which they excavate the various fossils. In the early days, with hurried traverses, there was a tendency to decide the relative ages of the fossils solely by their own peculiar features, without any exact observations in the field. The result was sometimes an argument in a vicious circle. As shown by the ovolume now before us, that is all changed. We find Detailed descriptions of specimens from the Permian of Texas, the Upper Cretaceous of Montana, the Eocene of Wyoming, and the Miocene of: ISB1 South Dakota. Accompanying them are well-illustrated exact accounts of all these formations and localities, determining the relative ages of the genera and species whjch were obtained from them.