The genus Retifusus was revised on the basis of conchological characters, radular morphology, foregut and stomach anatomy. Ten previously described and one new species are recognized as valid: R. jessoensis (Schrenck, 1863 in 1862-63), R. virens (Dall, 1877), R. olivaceus (Bartsch, 1929), R. laticingulatus (Golikov et Gulbin, 1977), R. roseus (Dall, 1877), R. parvus (Tiba, 1981), R. attenuatus (Golikov et Gulbin, 1977), R. similis (Golikov et Gulbin, 1977), R. iturupus (Golikov et Sirenko, 1998), R. latericeus (Möller, 1842), and R. latiplicatus sp. nov. Chrysodomus brunneus Dall, 1877 was synonymized with R. jessoensis; Bela yanamii Yokoyama, 1926 – with R. virens; Plicifusus saginatus Tiba, 1980 and Retifusus semiplicatus Golikov in Golikov et Scarlato, 1985 – with R. parvus.

The article contains additional data on the structure of the penial papillae and the atrial stimulators of the representatives of 13 species and subspecies of 8 (sub)genera of Ariantinae. The existence within the subfamily of five or six variants of structure of the copulative apparatus has been shown. Papilla of the penis or its elements can take on the role of stimulator; in such cases stimulator mostly is reduced down to full disappearance. Reproductive tract of some species has been re-described.

The genus Aulacofusus Dall, 1918 has been revised on the basis of conchological and available anatomical data. Nine previously described Recent species and one subspecies are recognised as valid: A. brevicauda (Deshayes, 1832), A. periscelidus (Dall, 1891), A. herendeeni (Dall, 1899), A. esychus esychus (Dall, 1907), A. esychus shikotanicus (Golikov et Gulbin, 1977), A. ombronius (Dall, 1919), A. calathus Dall, 1919, A. coerulescens Kuroda & Habe, 1961, A. hiranoi (Shikama, 1962), A. calamaeus (Dall, 1907). A. gulbini sp. n. is described, A. brevicauda fortilirata (Sowerby, 1913) has been synonymized with A. periscelidus (Dall, 1891). For 6 species, detailed descriptions of anatomy are provided. Twenty three species previously referred to Aulacofusus, have been excluded from the genus.

New findings of three gastropod species in Russian waters are discussed. Both Gibbula cineraria and Pseudosetia turgida were previously reported in Russian faunistic literature but absent in recent one. Haliella stenostoma is reported for the first time from Russian waters. Brief species descriptions are provided.

The problem of generic classification of the basommatophoran family Lymnaeidae Rafinesque, 1815 is reviewed as well as recent theoretical approaches to genus delineation in the zoological systematics. Two main versions of the generic system of lymnaeid snails are: 1) bigeneric approach where all diversity of lymnaeid species is split between two genera; and 2) polygeneric approach suggesting that there are several (about twenty) genera in the family. The first version is presented in systems developed by Kruglov and Starobogatov [1993] and Jackiewicz [1993, 1998]. The second one is most commonly accepted in current Western European and Northern American literature [Burch, 1989; Falkner et al., 2001; Glöer, 2002]. However, there are no grounds to delimit lymnaeid genera objectively as the solution critically depends on what taxonomic methodology (cladistic or ‘evolutionary’ taxonomy) is followed by a particular author. The ‘evolutionary’ taxonomic methodology (sensu Mayr) is favorable to the bigeneric approach, whereas the cladistic (Hennigian) methodology leads to the separation of a series of taxa of generic rank within Lymnaeidae. It is impossible to prefer one approach to another ultimately since the problem of acceptability of paraphyletic taxa is still not resolved. The co-existence of two different generic systems of the same family is therefore inevitable. Different criteria of generic rank were critically discussed in perspective of their applicability to lymnaeid taxonomy. The morphological and ecological criteria as well as the criterion of hybridizability proved to be controversial and their use gives no key to select one of these approaches. The fourth criterion, that of monophyly, is more usable now, when the data of molecular phylogenetics are available. The recent advances in molecular taxonomy of pond snails have been reviewed briefly. It seems very reliable that the family consists of two large monophyletic clades of deep origin that differ from each other by chromosome number albeit there are no morphological characters to distinguish surely between representatives of these clades. It is impracticable to assign the generic rank for these clades due to their huge internal heterogeneity (morphological and ecological). The most reliable cladistic solution is to regard the two deep lymnaeid clades as separate subfamilies each containing a set of genera that are internally homogeneous enough to comply with most of criteria of the genus rank. The scheme of lymnaeid classification proposed here includes the nominotypical subfamily Lymnaeinae (type genus Lymnaea Lamarck, 1799) with haploid chromosome number equal to 18 (rarely 19), and the new one Radicinae subfam.n. (type genus Radix Montfort, 1810). The latter taxon embraces genera and species of Lymnaeidae characterized by 16 or (most often) 17 chromosome pairs. Radicinae is, most probably, derived clade as compared to Lymnaeinae, however, there are no morphological synapomorphies to support it. The bigeneric system is, however, still acceptable for those who uses generic criteria proposed by “evolutionary systematics” such as “principle of the same degree of difference” [Golikov, Starobogatov, 1988] and others.

New investigations of freshwater habitats in caves revealed five new species of the Rissooidea in Bulgaria. The new species: Belgrandiella maarensis n. sp., Pontobelgrandiella tanevi n. sp. (the second species from this genus ever known), Bythiospeum simovi n. sp., Bythiospeum kolevi n. sp., Bythiospeum stoyanovi n. sp. are described and types illustrated. A synopsis of all published data on this ecological gastropod group in the country was compliled and complemented by author's unpublished data to provide a catalogue of all known Bulgarian stygobiotic and troglophilous freshwater snails with their localities.

A detail description of the shell and reproductive system of Elia novorossica is given and illustrated. The populations of this species on the Donetsk Upland in Ukraine are established as a new subspecies – E. novorossica nagolnica subsp. nov. Distribution and habitats of this subspecies are described in detail. Three populations of E. novorossica are currently known on Donetsk Upland, one of which is discovered for the first time. All these populations inhabit oak forests along the small rivers in the basin of the Nagolna river, in the highest part of upland. A conservation status of E. novorossica in Ukraine is considered as critically endangered, which is true for the new subspecies on the global level. Species composition of terrestrial molluscs in the locations of E.novorossica and on adjacent territories is adduced.

Carl Agardh Westerlund (1831–1908) was a prominent Swedish malacologist, who studied taxonomy and distribution of continental molluscs (terrestrial and freshwater). He established a number of new taxa, some of them are still accepted as valid. In this study, we provide information on type materials of 41 species of freshwater snails introduced by Westerlund and accepted in the current Russian taxonomy. The study is based on examination of materials from original Westerlund’s collection dispersed now among three large scientific institutions (Göteborgs Naturhistorska Museum, Swedish Museum of Natural History, and Zoological Institute of the Russian Academy of Sciences). For each species an account containing all relevant information on its type series is given. Taxonomic and nomenclatorial notes are also presented. For the majority of taxa, shells of type specimens are illustrated. The lectotypes for Limnaea truncatula var. sibirica Westerlund 1885, Planorbis dispar Westerlund 1871, Planorbis concinnus Westerlund 1881, Planorbis stroemi Westerlund 1881 and Physa sibirica Westerlund 1881 as well as the neotype for Planorbis borealis Lovén in Westerlund, 1875 are designated here.

The intricate history of Trophon birileffi Lischke, 1871 is analyzed. A lectotype is designated from 36 syntypes discovered in the Zoological Institute of the Russian Academy of Sciences in St. Petersburg, Russia. The species is redescribed and other specimens as well as the protoconch and the radula are illustrated. Two species, Sistrum alfredensis and Fusus pachyraphe formerly considered as synonyms of Trophon birileffi, are removed from its synonymy.

The information on reproductive characteristics of more than 100 species of the pulmonate molluscs (clutch size, egg size, hatching success, etc.) is summarized. It is shown that the pulmonates demonstrate a very wide range of reproductive strategies that serve to enhance the survival of species in different (sometimes very unfavorable) environmental conditions.

The problem of generic and subgeneric rank in Ariantinae is briefly discussed. A review of existing views on the system of non-helicine Helicidae (Ariantinae, Murellinae, and Thebinae) and differential diagnoses of the taxa are presented. Special attention is paid to the morphology of the atrial stimulator and, especially, penial papilla, because these organs play an important role in evolution of helicoid groups, providing the functioning of a pre-copulatory isolating mechanism.

Anatomical study has shown that the species described as Helix duporti Bavay et Dautzenberg, 1908 belongs to the genus Trachia Martens, 1860. A brief discussion of the problems of the taxonomy of snails having helicoid shells in the fauna of Vietnam.

В лабораторных условиях определен знак фототаксиса брюхоногого легочного моллюска Radix peregra (Müller, 1774). R. peregra показывает положительный фототаксис, который согласуется с его дневным типом активности и высоким уровнем освещенности мест обитания. Положительная реакция на свет обеспечивает моллюску нахождение мест обитания с благоприятными для жизнедеятельности световыми условиями и реализацию функции дыхания.

The visual acuity of a gastropod pulmonate mollusk Radix peregra (Müller, 1774) was estimated on the basis of phototaxis in the laboratory conditions. White cards with black vertical stripes of different angular width were used as visual stimuli. A value of the resolving angular distance of photoreceptors was 1-2°, and the calculated on its basis visual acuity -33-16.5 rad-1. The mollusc has a diurnal type of activity and lives at well-illuminated surface patches of ponds on aquatic caulescent plants that it feeds on. The results of behavioral investigation presented in this work and morpho-optical study of the eye carried out earlier allow to consider that R. peregra can identify caulescent plants, suitable for its inhabitation, feeding and travelling to the water surface.

The spectral sensitivity of the eye of a gastropod pulmonate mollusk Radix peregra (Müller,1774) was investigated on the basis of phototaxis in the laboratory conditions. The monochromatic light of tendifferent wavelengths in diapason 400-600 nm servedas a test stimulus. According to the results obtained R. peregra has monochromatic visual system with a possible visual pigment rhodopsin, that may be based on the retinal A and absorption maximum of which falls on a blue-green range of the spectrum about 490 nm.

Rare European species Pupilla pratensis is registered in the same calcareous fen in the Crimean Mountains, where Vertigo moulinsiana, another rare European species, was found earlier. Both species are known in Ukraine only from this one small site (less than 0.01 km2), which is disturbed and not protected, therefore both species are clearly “Critically Endangered” here. In the materials of Pupilla muscorum from Ukraine there are some unusual large specimens with shell width 1.9-2.0 mm were revealed, therefore these two species can’t be distinguished only by this characteristic, how it was partly considered before.

This paper presents the first data on seasonal quantitative dynamics of Gastropoda - dominant group of macrozoobenthos in three hydrodynamically different stony littoral areas of Lake Baikal. These studies were performed on the western shore of Southern Baikal (Cape Beryozovy) for 13 months in spring-autumn of 2002-2004. Species composition of gastropods varied with depth (1-20 m) from 10 to 17 species. Five species constantly inhabited the inshore area (depth 1-2,5 m), whereas in the wave-cut area (3-5 m) and the area of wave weakening (7-20 m) there were detected 6 species. During most of the investigation period, total density and biomass of gastropods was higher in the wave-cut area than that in two other regions of the lake. The rise of density and biomass of mollusks was recorded at all depth zones in autumn, whilst their quantitative values varied during other seasons. The main contributors to the total abundance of gastropods were Maackia herderiana and Choanomphalus maacki in the inshore area, whereas in the wave-cut area and area of wave weakening one species Maackia herderiana. Seasonal and inter-annual fauna dynamics of littoral gastropods was determined from changes in quantitative characteristics of species-dominants.

The structure of the distal parts of the reproductive system of the majority of the species of the genus Helicopsis occuring in Crimea and Black Sea Lowland (H. retowskii, H. dejecta, H. striata) were studied. The special attention was given to the intraspecific variability of the penial papilla shape and some proportions of the genitalia. Basing on the anatomical characters, the wide range of the conchological variability of H. retowskii has been shown. The area of this species goes out from limits of the Crimea. It is suggested that H. paulhessei (=H. gasprensis) and Xerophila elata are the synonyms of H. retowskii. The key for the determination of the Crimea molluscs of the genus Helicopsis on the anatomical characters is provided.

Anatomical study of the species described as Bradybaena boevi Uvalieva, 1967 has shown that this species does belong to the genus Bradybaena (Fruticicola in current sense). The contradictions in the literature, are related to the errors in the original description, in particular, Uvalieva took penial retractor for the flagellum.

An Illustrated description of the shell and reproductive tract of Pyramidula kuznetsovi is given. The presence of a distinct peripheral angle distinguishes this species from all known species of the genus. Both anatomically studied specimens had well-developed embryos in the uterus, whereas distal parts of the male section of reproductive tract were much reduced. Therefore it is hard to judge about anatomical differences of P. kuznetsovi from other species of the genus, in particular, the question on the presence of penial caecum remains open.