Iceland.—Eleven species, all Scandinavian, occur. These are Arion 2, Limax 1, Helix 2 (arbustorum L. and hortensis Müll., the latter being found only on the warmer southern coast), Limnaea 1, Planorbis 1, Pisidium 4.
France.—The northern, central, and eastern districts belong to this sub-region, while the southern and western, in which an entirely new element occurs and many northern forms disappear, belong to the Mediterranean. Thus, for instance, Helix pomatia L., H. incarnata Müll., H. fruticum Müll., H. cantiana Mont., H. strigella Drap., H. rufescens Penn., H. plebeia Drap., are not found in southern France. No detailed enumeration of species is at present possible, the efforts of a large number of the leading French authorities being directed to indiscriminate species-making rather than to the careful comparison of allied forms. Perhaps the principal difference between the Mollusca of northern France and those of our own islands is the occurrence of two species of Pomatias. In the more elevated districts of eastern France (the Vosges, Jura, western Alps), a certain number of species occur which are confined to the high grounds of south central Europe. Among these are Helix holoserica Stud., H. personata Lam., H. bidens Chem., H. depilata Drap., H. cobresiana Alt., H. alpina Faure.
The Pleistocene deposits of the valley of the Somme tell the same tale as those of eastern England, containing as they do species and even genera whose northern range is now much more limited. The Eocene fossils from the Paris beds show most remarkable relationships to genera now existing in the West Indies and Central America. Others again indicate affinities with India. Thus we find Ceres, Megalomastoma, and Tudora by the side of Leptopoma, Faunus, and Paludomus.
Germany.—The Mollusca of the plains of northern Germany are few and not striking, and exhibit little difference from those of our own islands. In the mountainous districts of the south and south-east, a number of new forms occur, amongst which are 3 species of Daudebardia, a remarkable carnivorous form, with the general appearance of a Vitrina; 24 of Clausilia, many Pupa, several Buliminus, 3 of the Campylaea group of Helix, stragglers from the Italo-Dalmatian fauna, and 1 of Zonites proper. Our familiar Helix aspersa is entirely absent from Germany. There are only 4 land operculates—Pomatias 2, Acicula 1, Cyclostoma 1, all of which occur exclusively in the south. Bithynella and Vitrella, two minute forms of fresh-water operculates akin to Hydrobia, occur throughout the district.
Fig. 193.—A, Daudebardia brevipes Fér.: sh, shell; p.o, pulmonary orifice. (After Pfeiffer.) B, shell of D. rufa Pfr., S. Germany.
Northern Russia and Siberia.—This vast tract extends from eastern Germany to the Amoor district. It is exceedingly poor in Mollusca, and is chiefly characterised by the gradual disappearance, as we proceed eastward, of European species. There are a few characteristic Siberian Mollusca, closely allied to European forms, and in the extreme east a new element is introduced in the appearance of types which indicate Chinese affinities. The whole district may be regarded as bounded to the south by a line drawn from Lemberg to Moscow, and thence to Perm; passing south of the Ural mountains, it includes the whole basins of the rivers Obi, Yenesei, and Lena, coinciding with the vast mountain ranges which terminate to the north the table-land of central Asia, at the eastern extremity of which it dips sharply southwards, so as to include the Amoor basin and Corea.
All the larger Helices are wanting, and no land operculates occur. Helix arbustorum L., H. nemoralis Müll., H. lapicida L., H. aculeata Müll., and Hyalinia nitidula Drap., do not appear to occur east of the Baltic; Arion fuscus Müll., Helix strigella Drap., Buliminus obscurus Müll., Clausilia laminata Mont., C. bidentata Bttg., C. plicatula Drap., Viviparus fasciatus Müll., and Neritina fluviatilis L., do not pass the Urals.
In the Obi district (West Siberia) a further batch of European species find their easterly limit. Among these are Helix hispida L., Bithynia tentaculata L., Vivipara vivipara L., Pisidium amnicum Müll., and Unio tumidus Retz. A few distinctly Siberian species now appear, e.g. Ancylus sibiricus Gerst., Valvata sibirica Midd., and Vitrina rugulosa Koch.
The following are among the European species which reach eastern Siberia: Hyalinia nitida Müll., Succinea oblonga Drap., Planorbis vortex L., spirorbis L., marginatus Drap., rotundatus Poir., fontanus Light., Valvata piscinalis Müll., Bithynia ventricosa Leach, and Anodonta variabilis Drap. Here first occur such characteristic species as Physa sibirica West., P. aenigma West., Helix pauper Gld., H. Stuxbergi West., H. Nordenskiöldi West., Planorbis borealis Lov., Valvata aliena West., Cyclas nitida Cless., and C. levinodis West. In the Amoor district a decided Chinese element makes its appearance in a few hardy forms which have penetrated northward, e.g. Philomycus bilineatus Bens., and a few each of the Fruticicola (Chinese) and Acusta groups of Helix. Out of 53 species, however, enumerated from this district, as many as 33, belonging to 18 genera, occur also in Great Britain.