71. A, FRONT PART OF BODY OF A PRAWN (_Spirontocaris polaris_), FROM ABOVE, SHOWING ON THE RIGHT SIDE A SWELLING OF THE CARAPACE CAUSED BY THE PRESENCE OF THE PARASITE _Bopyroides hippolytes_ IN THE GILL CHAMBER; B, THE FEMALE PARASITE EXTRACTED AND FURTHER ENLARGED; C, THE MALE PARASITE ON SAME SCALE AS THE FEMALE 222 72. A FISH-LOUSE (_Caligus rapax_), FEMALE. × 5 225 73. STAGES OF DEVELOPMENT OF _Lernæa branchialis_. F IS SLIGHTLY, THE OTHER FIGURES GREATLY, ENLARGED 226 74. STAGES OF THE LIFE-HISTORY OF _Hæmocera danæ_, ONE OF THE MONSTRILLIDÆ 229 75. FREE-SWIMMING STAGES OF _Sacculina carcini_. MUCH ENLARGED 232 76. EARLY STAGE OF _Sacculina_ WITHIN THE BODY OF A CRAB 234 77. ROSTRUM AND FORE PART OF CARAPACE, SEEN FROM ABOVE, OF (A) RED-CLAWED CRAYFISH (_Astacus fluviatilis_) AND (B) WHITE-CLAWED OR ENGLISH CRAYFISH (_Astacus pallipes_) 242 78. THE COMMON SHRIMP (_Crangon vulgaris_). NATURAL SIZE 244 79. THE NORWEGIAN DEEP-WATER PRAWN (_Pandalus borealis_), FEMALE 246 80. THE GRIBBLE (_Limnoria lignorum_). MUCH ENLARGED 254 81. RESTORATION OF A TRILOBITE (_Triarthrus becki_), SHOWING THE APPENDAGES. UPPER SIDE ON RIGHT, UNDER SIDE ON LEFT. SLIGHTLY ENLARGED 258 82. _Ceratiocaris papilio_, ONE OF THE FOSSIL PHYLLOCARIDA 262 83. _Pygocephalus cooperi_, FROM THE COAL-MEASURES: UNDER SIDE OF A FEMALE SPECIMEN, SHOWING THE OVERLAPPING PLATES OF THE BROOD-POUCH 263 84. THE TASMANIAN "MOUNTAIN SHRIMP" (_Anaspides tasmaniæ_), A LIVING REPRESENTATIVE OF THE SYNCARIDA. SLIGHTLY ENLARGED 264 85. _Præanaspides præcursor_, ONE OF THE FOSSIL SYNCARIDA, FROM THE COAL-MEASURES OF DERBYSHIRE. SLIGHTLY ENLARGED 265 FULL-PAGE PLATES PLATE FACING PAGE I. MALE AND FEMALE LOBSTERS, SHOWING THE DIFFERENCE IN THE RELATIVE BREADTH OF THE ABDOMEN IN THE TWO SEXES. THIS FIGURE ALSO ILLUSTRATES THE DISSIMILARITY OF THE LARGE CLAWS, AND THE FACT THAT THE "CRUSHING CLAW" MAY BE ON EITHER THE RIGHT OR LEFT SIDE OF THE BODY. (_From Brit. Mus. Guide_) 26 II. _Apus cancriformis_ FROM KIRKCUDBRIGHTSHIRE. SLIGHTLY ENLARGED 36