EXPLANATION OF PLATE I. 



Fig. 1. Ceriodaphnia dentata, fern. Head x 80. 



2. " " " Post-abdomen X 130. 



3. " consors, " Head X 80. 



4. " " " Post-abdomen X 130. 



5. Simocephalua vetulus, " Macula nigra X 260. 



6. " Americanus, fern. Macula nigra X 260. 



7. Scapholeberis mucronata, fern. Head from below X 160. 



8. " nasuta, male. Head seen obliquely from below X 260. 



9. " " fern. Head X 80. 



10 ; 10 a. " " fern. Macula nigra from side and from be- 



low X 260. 



11. Daphnia pulex. Terminal claw. 



12. Macrotlirix rosea, male. Post-abdomen X 260. 



13. " " " Antennule X 260. 



14. Alonopsis media, " Post-abdomen X 160. 



15. " " fern. " X 150. 



16. Alona porrecta, male. X 150. 



17. Graptoleberis inermis, fern. Post-abdomen X 150. 



18. Crepidocercus setiger, fern. X 148. 



19. Pleuroxus procurvus, fern. Front part of animal X 150. 



20. " " fern. Hind part of valve X 150. 



21. " denticulatus, fern. Post-abdomen X 150. 



22. " unidens, fern. Hind part of body and valves X 95. 



