Study of the reproductive tract of Helix pseudomiara Bavay et Dautzenberg, 1908, formally attributed to the genus Trachia, and its comparison with other anatomically studied species of the genus, made it necessary to reconsider the taxonomic structure of the taxon. It is shown that four species, whose anatomy is known, belong to four genera, differing both conchologically and anatomically. Descriptions and diagnoses (based on their type species) of genera Trachia Martens, 1860 (type species Helix asperella Pfeiffer, 1846), Bellatrachia gen. nov. (type species Helix pseudomiara Bavay et Dautzenberg, 1908), Pseudotrachia gen. nov. (type species Helix vittata Müller, 1774), and Neotrachia gen. nov. (type species Helix duporti Bavay et Dautzenberg, 1908) are presented.

This paper summarizes the mechanisms behind the patterning of the intra-population spatial arrangement of the land snail Vallonia pulchella (Müller, 1774) in terms of edaphic and vegetation properties. The molluscs were collected from a regular grid in recultivated soil (the research station of Dnipro State Agrarian and Economic University, Pokrov, Ukraine). As predictors of the snail population abundance, spatial variables were used, as well as edaphic and vegetation indices. It is shown that V. pulchella to prefer microsites characterized by higher soil electrical conductivity, which contain larger aggregate fractions with low mechanical impedance and the low temperature at the depth of 0-10 cm, with a more developed dead plant layer, low-light and low hygromorph and heliomorph index values of the vegetation.

Three new species of the genus Stenosemus collected near Fiji and Solomon Islands of the central Pacific are described here. Stenosemus fijiensis sp. nov. from Fiji differs from the congeneric species by a unique sculpture of the central areas of tegmentum, consisting of triangular pits and light brown spots on valves. S. philippei sp. nov. and S. solomonensis sp. nov., both from the Solomon Islands, differ from other the species of the genus by having a head of major lateral tooth of radula bicuspidate with small outer denticle, shape and sculpture of dorsal spicules and sculpture of tegmentum.

Bela arctica A. Adams, 1855 has a complicated and confusing taxonomic history. Grant and Gale [1931] considered “Defrancia viridula Fabricius” Møller, 1842, Bela kobelti Verkrüzen, 1876, “Bela viridula Møller” G.O. Sars, 1878, and Lora tenuilirata cymata Dall, 1919 as its synonyms. It is demonstrated that Propebela arctica sensu Grant and Gale is a group of six species belonging to four genera. It is proposed to consider the following species as separate: Propebela arctica (A. Adams, 1855); Curtitoma finmarchia (Friele, 1886) comb. nov. [=“Defrancia viridula Fabricius” Møller, 1842]; Curtitoma georgossiani sp. nov. [=“Bela viridula Møller” G.O. Sars, 1878 (part)]; Granotoma kobelti (Verkrüzen, 1876) comb. nov., Granotoma tumida (Posselt, 1898) comb. nov. [=“Bela viridula Møller” G.O. Sars, 1878 (part)], and Obesotoma cymata (Dall, 1919). In addition, in this work for the first time Curtitoma livida comb. nov. is recorded from Russian waters.

On the Kugitangtau Ridge (western part of Pamiro-Alai mountain system) 16 specimens of a new species of molluscs referring to the nominative subfamily of the Bradybaenidae family have been found. The new taxon differs from all other species of this subfamily by total absence of all additional organs of female section of the reproductive tract (stylophore, additional sac, mucus glands, supraatrial bladder), bean- shaped short penis, and thick-walled penis sheath that attached at both proximal and distal ends. On the base of these characters the illustrated description of a new monotypic taxon Kugitangia hatagica Schileyko, Pa- zilov et Abdulazizova, gen. et sp. nov. is presented. Conchologically the new species does not differ reli- ably from Fruticicola fedtschenkoi and differs from Fruticicola perlucens mainly by the presence of fine granulation on the embryonic whorls.

 In accordance with the taxonomic system adopted in Russia and used also in Estonia, the largest local forms of pea clams (Sphaeriidae) have been treated as two species, P. amnicum and P. inflatum. The aim of the study was to clarify if P. amnicum and P. inflatum are separate species. Populations of both forms from Estonia were analysed genetically and morphologically. Analysis of the COI and ITS-1 gene fragments revealed that these two forms were genetically indistinguishable. Although there were statistically significant differences in the relative proportions of the shell between their typical individuals, there occurred also intermediate values. Consequently, P. inflatum cannot be considered as a separate species and should be treated as an ecological variety of P. amnicum that inhabits mainly a characteristic sandy substrate.

Development of the larval and juvenile shells of the White Sea bivalve Zirfaea crispata has been studied. The main stages of shell development from D-stage to early juveniles were described. The formation of larval hinge, consisting of two small teeth on the left valve and two teeth of different size on the right valve was observed. The complex shape of the large tooth on the right valve was noted at the pre- metamorphosis stages. Development of a structure, typical for certain Pholadidae – an articular connection on the ventral edge of the shell was recorded. This connection consists of a rectangular tooth on the right valve and a depression, flanked by small projections, on the left valve. The ventral connection starts to form at the larval size of 300 µm and becomes fully formed prior to metamorphosis. After metamorphosis the ventral connection does not disappear, but continues to grow with the growing edge of dissoconch. The role and functional importance of this structure in Zirfaea is discussed.

New findings of four gastropod species: Melanella laurae, Hemiaclis ventrosa (family Eulimidae), Chrysallida sublustris and Odostomia acuta (family Pyramidellidae) are described. O. acuta was previously confused by Russian authors with H. ventrosa, distribution of both species in the Barents Sea is limited by the coastal waters of Finmark and Murman. M. laurae and C. sublustris were found for the first time in the adjacent to the Barents Sea parts of the Arctic Ocean.

Based on the study of the reproductive tract of Metafruticicola occidentalis Subai, 1999, it is shown that the species belongs to a new subgenus (Elbasania subgen. nov.). For comparison, the anatomy of seven species of the genus Metafruticicola (including type species) has been studied. It is shown that the species of this genus are clearly distinguished from one another by the structure of the copulative apparatus (mainly of penial papilla). Comparison of the genus Metafruticicola with the representatives of other genera of Hygromiidae that have no accessory organs on the vagina is conducted. We suggest that the genus Cyrnotheba Germain, 1929 may belong to the subfamily Metafruticicolinae while the genus Caucasocressa does not belong to this subfamily and might be included in the subfamily Monachainae. Problems of taxonomic structure of the genus Metafruticicola briefly discussed.

Limax flavus Linnaeus, 1758 not previously recorded in Central Asia was found in Uzbekistan. The total number of adventitious species in Central Asia is 12; six species are migrants from Asia (Caucasus); six from Europe. Nine species were found before 1990, while three after 1991. Of these seven species are slugs (58%); nine of adventitious species are kolonozoids, three – epecozoids.

In 2015-2016 land molluscs from 43 localities in Ararat Region, Vayots Dzor Region and Kotayk Region as well as in Yerevan were investigated. The introduced species Monacha fruticola and Oxychilus cf. filicum were first discovered on the territory of Armenia. One new locality of the rare species Orculella ruderalis, listed in the Red Book of Armenia, was found. The some pecularities of the intraspecific variability of the shells of O. ruderalis and Pseudochondrula tetrodon were described.

Three species, attributed to buccinid genus Plicifusus, had been previously known from the Arctic: Plicifusus kroeyeri (Møller, 1842), P. johanseni Dall, 1919, and P. rodgersi (Gould, 1860). Study of museum collections and recently obtained material from the Laptev and East Siberian seas resulted in discovery of Plicifusus maehirai Tiba, 1980, previously known from the Northern Pacific, and Plicifusus sp., which probably belongs to an undescribed species. P. johanseni has been found in the Russian waters for the first time. Lectotype of P. johanseni has been designated.

In the paper of Merkuljev A.V. 2017. “Taxonomic puzzle of Propebela arctica (A. Adams, 1855) (Gastropoda, Mangeliidae) – six different species under single name”, published in vol. 27(1): 15-30 the misprint has been found. On p. 26 in the caption to Fig. 5, the 9-th line from the bottom, instead of “C. georgossiani sp. nov. C. The holotype, ZIN 21768/1” read “C. georgossiani sp. nov. C. Paratype, ZIN 51254/2.”

On the basis of dissections and shell measurements we studied sexual dimorphism in shell shape in Parafossarulus manchouricus (Gerstfeldt in Bourquignat, 1860) taken from the bay of the Bira River (Russian Far East). It is shown that there are no statistically significant differences in shells of males and females in P. manchouricus.

In 2015-2016 land molluscs from 48 natural and anthropogenically transformed localities in Syunik Region of Armenia were investigated. The analysis of our and literature data gave the possibility to draw up a species list of land molluscs of Syunik Region, which includes 78 species. Two forms with unclear taxonomic status are described: Stenomphalia sp. and Chondrula cf. sunzhica.

The population structure of the terrestrial mollusc Brephulopsis cylindrica (Gastropoda, Pulmonata, Enidae) in the native area (Crimea Peninsula) and out of its borders (two adventive groups in the city of Belgorod) was studied on the basis of conchometric characteristics and analysis of polymorphic allozyme loci. For all the morphometric parameters statistically significant differences were found between the studied groups. In all studied populations a high level of intrapopulation genetic variability was revealed (Fit = 0,401). At the same time, the considerable variability of the conchological parameters and the high level of allelic polymorphism at a number of loci identified in adventitious colonies create the prerequisites for successful adaptation to new conditions and further expansion of the species range in urbanized areas. 

Morphological properties of the granules of the screening pigment in the retinae of camera eyes of gastropod mollusks with different light preferences were studied. It was demonstrated that the pigment granules of mollusks can differ by color and size but do not differ by structure, electron density and form. Light conditions of mollusks’ habitats can influence on the amount of the screening pigment, which in its turn does not affect resolving ability of the eyes.

Two doubtful cases of species name replacements in the family Lymnaeidae Rafinesque, 1815 (pond snails) proposed in 1990–2000s are discussed. These are: Radix labiata (Rossmäßler, 1835) vs. R. peregra (O.F. Müller, 1774), and Stagnicola fuscus (C. Pfeiffer, 1821) vs. S. vulneratus (Küster, 1862). It is shown that in both instances the name alterations were not based on the conclusive evidence and thus seem to be proposed without substantial reasons. I argue that the name Radix peregra cannot be ruled out and replaced by R. labiata. The type series of the latter has been identified in collection of the Natural History Museum of Vienna and it is shown that R. labiata is a junior synonym of R. balthica (Linnaeus, 1758). The lectotype of Limnaeus pereger var. labiatus Rossmäßler, 1835 is designated. The resurrection of the species name Limnaeus fuscus (Pfeiffer, 1821) for application to a certain species of Stagnicola is also very doubtful since this name must be treated as a nomen dubium, and any taxonomic interpretation of it is inevitable based on more or less reliable hypothesis, not on the total evidence. The replacement of S. vulneratus by its alleged senior synonym adds little to our knowledge on lymnaeid taxonomy and evolutionary relationships. It is desirable that the nomenclatorial principle of priority must not be applied to nomina dubia.

New data on the record of synanthropic species of slugs Limacus flavus and Krynickillus melanocephalus in Belarus are analyzed. It is assumed that the penetration of these species into the territory of Belarus occurred from their natural habitats anthropochory way together with the imported vegetable products.

Acrotoma (Castelliana) likharevi sp. nov., Acrotoma (Castelliana) reshaviensis sp. nov., and Micropontica (Baleopsina) olgae sp. nov. are described from the Bzyb Mountains of Abkhazia. The taxonomic position, relation to congeneric taxa, and zoogeographical significance of the new taxa are discussed.