_D. ovocaudatum_ Species of _Planorbis_ Probably omitted. Vulp. _Rana esculenta_ (_Cercaria_ known as _C. cystophora_ Wag.) _D. retusum_ _Rana_ _Limnaea stagnalis_ _L. stagnalis_, larvae Duj. of Phryganeidae _D. squamula_ Polecat Unknown _Rana temporaria_ Dies. _D. signatum_ _Tropidonotus Unknown _Rana_ Duj. natrix_ _D. trigonocephalum_ _Paludina vivipara_ Rud. Badger, Polecat Unknown Dogfish, Rays _Ostrea edulis_, _Belone vulgaris_ _Gasterostomum_ sp. _Cardium rusticum_, _C. edule_ _Unio_, _Anodonta_ _G. fimbriatum_ (_Cercaria_ known _Leuciscus v. Sieb. _Perca_, _Esox_ as _Bucephalus erythrophthalmus_ polymorphus_) _G. gracilescens_ Unknown Species of _Gadus_ Rud. _Lophius piscatorius_ (e.g. _G. aeglefinus_), _Molva_, _Lophius_ _Monostomum flavum_ _Planorbis corneus_ Mehl. _Anas_ Omitted CLASSIFICATION OF TREMATODES.—We have seen (p. 63) that it is hardly possible to carry out fully the division of Trematodes into Monogenea and Digenea. Nevertheless, pending further investigation on the doubtful points, this classification may still be {73}used. Monticelli[93] has proposed the main divisions of a new classification, which has been also adopted by Braun, and is based on the nature of the suckers. These divisions are indicated below in brackets.