398 Wisconsin Academy of Sciences, Arts and Letters. 



mals can be gathered from a long distance, before the dredge fills. The, 

 cone not only excludes weeds but also keeps out insects, larvae, large 

 Gammari, etc., which so abound in localities favorable for Cladocera, and 

 whose size and activity made it difficult to distinguish the smaller Crus- 

 tacea in the collector's jar. The fact that this dredge can be pulled 

 through weeds and strain a large quantity of water without obtaining 

 a large amount of vegetable debris makes it very valuable in obtaining 

 the rarer Cladocera . 



The dredge is emptied by unscrewing the screw-cap and washing out the 

 contents of the bag into a tumbler or small jar of water. In collecting 

 near home this is brought to the laboratory for study. When it is de- 

 sired to preserve collections for future study, the water is allowed to 

 stand and settle for a short time and then the clear water containing the 

 animals and free from mud is poured through a funnel into a small bag 

 of cheese-cloth which is tied and put into alcohol or other preserving 

 fluid. 



With this dredge it is not at all difficult to collect 20-30 species of 

 Cladocera from one locality and in a few hauls. In a collection thus 

 gathered from the shore on a flying trip to some small lakelets at Man- 

 istee, Mich., I found twenty-six species of littoral Cladocera. Zacharias* 

 in a summer's campaign in North German lakes found only twenty-three 

 species from the shore waters. 



PLATE XIII. 



Fig. 1. Latonopsis occidentalism Birge. Head of male, enlarged 60 diameters. 



Fig. 2. " " Head of young female, enlarged 50 diameters. 



Fig. 3. " " Post-abdomen of male, enlarged 75 diameters. 



The spines of the carapace are omitted. 

 Fig. 4. " " Antennule of new-hatched male, enlarged 200 



diameters. 

 Fig. 5. " " First leg of male, enlarged 175 diameters. 



Fig. 6. Latona setifera, O. F. M. Male antennule to show position of appendix cili- 



ata (a). Enlarged 200 diameters. 

 Fig. 7. Daphnia retrocurva, Forbes. Male antennule, enlarged 200 diameters. 

 Fig. 8. " " Female, enlarged 30 diameters. 



Fig. 9. " hyalina, Leyd. Male antennule, enlarged 200 diameters. 



Fig. 10. Ophryoxus gracilis, Sars. Head of male, enlarged 65 diameters. 

 Fig. 11. " " Post-abdomen of male, enlarged 160 diameters . 



Fig. 12. " " Part of first leg of male, enlarged 200 diameters. 



Fig. 13. Macrothrix rosea, Jur. Antennule of male, enlarged 240 diameters. 

 Fig. 14. " " Post-abdomen of male, enlarged 240 diameters. 



Fig. 15. Drepanothrix dentata, Eur. Post-abdomen of male, enlarged 175 diameters. 

 Fig. 16. " " Female, enlarged 65 diameters. 



Fig. 17. " " First leg of male, enlarged 300 diameters. 



Fig. 18. Ilyocryptus longiremis, Sars. Male, enlarged 100 diameters. The spines of the 



carapace are omitted where they would cross 



the post-abdomen. 

 Fig. 19. Alona lepida, Birge. Cast shell to show markings, enlarged 60 diameters. 

 Fig. 20. Dunhevedia setiger, Birge. Male, enlarged 115 diameters. 

 Fig. 21. Pleuroxus denticulatus, Birge. Post-abdomen of male, enlarged 165 diameters. 



* Zacharias, O. Zur Kenntniss der pelagischen und littoralen Fauna Norddeutschen Seen, 

 Zeit. Wiss. Zool. Vol XLV, 1887., p. 265. 



