14 Illustrations 



FACE 



37 Head of lamprey, and sucker showing scars made by lamprey 109 



38 Lungfish and fossil shark, Cladoselachc 112 



39 A trilobite 117 



40 A king crab 117 



41 Ostracoderms 118 



42 Cestracion, Polyterus and Hatteria 121 



43 Footprint of a primitive am[)liihi;in 122 



44 A stcgoccphalan 123 



45 Landscape of the coal-forming period 124 



46 Dinosaur tracks 126 



47 Brontosaurus 127 



48 Stegosaurus 128 



49 Triceratops 128 



50 Rhamphorhynchus 129 



51 Arc'ha'opteryx 131 



52 Hesperornis 132 



53 Part of feather, showing details 133 



54 Tooth of dinosaur and jaw of contemporary mammal . . . 137 



55 Opossum 138 



56 Spiny ant-eater 139 



57 Uintatherium, Coryphodon, and Dromocyon 141 



58 Eohippus 143 



59 The tarsier 144 



60 The saber-toothed tiger 146 



61 Excavation of a tar pit at Rancho La Brea, California . . . 148 



62 Early days in the tar pools of Southern California .... 149 



63 The arctic tern 152 



64 A group of lichens 159 



65 A glacial pond 160 



66 Zoogeographical realms 161 



67 Life zones of North America 162 



68 Profile of San Francisco Mountain, showing life zones . . . 163 



69 An alpine dwarf 164 



70 Pika, or Rocky Mountain hare 165 



71 Ptarmigan in summer plumage 166 



72 Ptarmigan in autumn plumage 166 



73 Ptarmigan in winter plumage 167 



74 Clarke's crow 167 



75 Timber line in the Rocky Mountains 168 



76 Polar bears 169 



77 Cariboo 169 



78 Musk oxen 170 



79 Wolverine 170 



80 Canadian zone forest in Colorado 171 



81 Woodchuck 172 



82 Weasel 173 



83 Snowshoe rabbit 173 



