BRITISH FRESHWATER FAUNA 167 



sea to the comparatively scanty fauna of our rivers and 

 akes. 



The freshwater fauna of our own islands, though fairly 

 representative, could almost be written on a sheet of 

 notepaper. The following list, though very incomplete, is 

 sufficient for our purposes : 



VEKTEBEATA. MAMMALS : Otter, Water-vole. 

 BIKDS : Ducks and other web-footed fowl. AMPHIBIA : 

 Newts and tadpoles of frogs and toads. FISH : Bony fish 

 with spiny fins : Perch, Miller's Thumb, Blenny, 

 Gudgeon. With soft fins : Berbot, Carp, Bream, Roach, 

 Dace, Tench, Chub, Minnow, Salmon, Shad, Eel. Cyclo- 

 stomes : Lamprey. 



IN VEETEBEATA. INSECTS : Beetles : Dytiscus 

 (Fig. 53), Gyrina, and others. Bugs : Water-boatman 

 (Notonecta), Water-scorpion (Nepa) , and others. Neurop- 

 tera, larvae of dragon flies, caddis flies, and many others. 

 Flies : larvse of gnats and daddy-long-legs. SPIDEES, 

 Water-mites and others. Tardigrades : Water bear. 

 CRUSTACEA : Decapods, Crayfish. Isopods : Asellus 

 (water-hog-louse). Amphipods : Freshwater shrimp 

 (Gammarus), &c. Phyllopods : Estheria, Branchipus. 

 Cladocera : Water-fleas (Daphnia). Ostracoch : Cypris. 

 Copepods : Cyclops. Siphonostoma : Fish-lice. WORMS. 

 Leeches : Clepsine, Nephelis, Piscicola, Branchiobdella. 

 Chcetopods: Tubifex, Stylaria, Nais. Nematodes, Cestodes, 

 Trematodes, Nemertines. MOLLUSCS : Lamellibranchs 

 (Bivalves) : Unio, Anodoiita, Cyclas, Pisidium, Dreissena. 

 Gasteropods (Univalves) : Neritina, Paludina (Fig. 55), 

 Bithynia, Valvata (Fig. 69), Limnsea (Fig. 56), Physa, 

 Planorbis, Ancylus (Fig. 75). EOTIFERS : a vast number 

 (Fig. 61). POLYZOA: Cristatella, Pectinatella, Lophopus, 

 Alcyonella, Plumatella (Fig. 48), Fredicella, Paludicella, 

 Urnatella, Victorella. TURBELLARIA : Planaria, Poly- 



