Differences between Mastodon and Mammoth, 198; affinities of the Mastodon, 200; vestigial structures, 201; distribution of American Mastodon, 203; first noticed in North America, 204; thought to be carnivorous, 206; Koch's Missourium, 208; former abundance of Mastodons, 209; appearance of the animal, 210; its size, 211; was man contemporary with Mastodon? 213; the Lenape stone, 215; legend of the big buffalo, 216; references, 218. XII. WHY DO ANIMALS BECOME EXTINCT? Extinction sometimes evolution, 221; over-specialization as a cause for extinction, 222; extinction sometimes unaccountable, 223; man's capability for harm small in the past, 224; old theories of great convulsions, 226; changes in nature slow, 227; the case of Lingula, 228; local extermination, 229; the Moas and the Great Auk, 232; the case of large animals, 233; inter-dependence of living beings, 234; coyotes and fruit, 236; Shaler on the Miocene flora of Europe, 236; man's desire for knowledge, 238. INDEX, 243 NOTE ON THE ILLUSTRATIONS The original drawings, made especially for this book, are by Charles R. Knight and James M. Gleeson, under the direction of Mr. Knight. The fact that the originals of these drawings have been presented to and accepted by the United States National Museum is evidence of their scientific value. Mr. Knight has been commissioned by the Smithsonian Institution, the United States National Museum, and the New York Museum of Natural History, to do their most important pictures of extinct animals. He is the one modern artist who can picture prehistoric animals with artistic charm of presentation as well as with full scientific accuracy. In this instance, the author has personally superintended the artist's work, so that it is as correct in every respect as present knowledge makes possible. Of the minor illustrations, some are by Mr. Bruce Horsfall, an artist attached to the staff of the New York Museum of Natural History, and all have been drawn with the help of and under the author's supervision. LIST OF ILLUSTRATIONS Fig. Page Phororhacos, a Patagonian Giant of the Miocene _From a Drawing by Charles R. Knight_ _Frontispiece_ 1. Diplomystus, an Ancient Member of the Shad Family _From the fish-bed at Green River, Wyoming. From a specimen in the United States National Museum._ 4 2. Bryozoa, from the Shore of the Devonian Sea that Covered Eastern New York _From a specimen in Yale University Museum, prepared by Dr. Beecher._ 10 3. Skeleton of a Radiolarian Very Greatly Enlarged 17 4. Cephalaspis and Loricaria, an Ancient and a Modern Armored Fish 24