LIST OF ILLUSTRATIONS xv 



FIG. PAGE 



53. A Water Beetle (Dytiscus) Carrying a Bivalve Shell . . 181 



54. The Free-Swimming Larva of Drc.issena polymorpha . 182 



55. Paludina vivipara ....... 183 



56. Limned stagnalis ...... 184 



57. The Development of the Gemmule of a Freshwater Sponge 



(Ephidatia fluviatilis) ...... 185 



58. Eggs of Hydra riridis and H. grisea .... 186 



59. Statoblasts of a Polyzoon (Plumatella fruticosa) . . .187 



60. Statoblast of a Polyzoon (Cristatella mucedo) . . . 188 



61. A Tube-making Rotifer (Floscularia longicaudata) . . 190 



62. The Winter Egg, or Epihippium, of Water-Fleas . . 191 



63. Apus cancriformis, a Freshwater Crustacean . . . 192 



64. The Freshwater Prawn (Palcemon serratus) . . . 193 



65. A Marine Prawn (Peneus) . . . . . .193 



66. The Development of the Marine Prawn (Peneus}, Nauplius 



and Zoea Stages ...... 194 



67. Further Development of Peneus, the Mysis Stage . . 195 



68. Air-breathing Shells from the Carboniferous System of North 



America ....... 197 



69. Valvata piscinalis ....... 199 



70. Goniobasis sp., Fascinella, and Syrnolopsis . . . 203 



71. Stomatopsis, a Freshwater Shell from the Cosina Beds of Istria 204 



72. Congeria, from the Pontic Beds ..... 205 



73. Melanopsideee, from the Miocene and Pliocene Beds . . 206 



74. Transformation of Paludina by the Influence of Brackish Water 207 



75. The Freshwater Limpet (Ancylus) ..... 208 



76. The Freshwater Jelly-fish (Limnocodium victoria) . . 209 



77. Tiphobia Horei, from lake Tanganyika .... 210 



78. Pyrgulifera and Paramelania ..... 212 



79. Paludinas from the Laramie Beds and lake Tanganyika . . 214 



80. Steno's Figure of the Head of a Shark .... 222 



81. Successive Stages in the History of Tuscany as Represented by 



Steno . . . . . . . .226 



82. Section across England and Wales .... 261 



83. Temperature Curve for the British Isles during the Tertiary JEra 269 



