2 Bulletin American Museum of Natural History [Vol. XLI1 



6. Sphercheinse 30 



7. Hydrophilinse 31 



Hydrophilus (PL VI) 31 



H. obtusatus 31 



Tropisternus (PL VII) 35 



T. glaber 35 



T. sublcevis ? 39 



Hydrous (PL VIII) 39 



H. triangularis 40 



8. Hydrobiinse 42 



Laccobius (PL IX) 43 



L. agilis 43 



Berosus (PL X) 47 



B. peregrinus : 48 



B. striatus 51 



Choetarthria 51 



Hydrobius (PL XI) 51 



H . globosus 52 



H . fuscipes 55 



H. tesselatus 55 



H. scabrosus 55 



Helocombus : 56 



Cymbiodyta (PL XII) 56 



C. fimbriata ■ 57 



C. blanchardi 61 



Helochares (PL XIII) 61 



H. maculicollis 62 



H . normatus 65 



Philydrus (PL XIV) 65 



P. perplexus 67 



P. nebulosus 69 



P. ochraceus 70 



P. cinctus 70 



P. hamiltoni 70 



Anccena (PL XV) 71 



A. infuscata 71 



Paracymus (PL XVI) 74 



P. subcupreus 74 



9. Sphseridiinas 77 



III. Phylogenetic Considerations 77 



IV. Keys 82 



Egg-cases 82 



Larvse 83 



Pupse 87 



V. Literature 88 



