The generic name Cryptobranchia Middendorff, 1851 is a junior objective synonym of Lepeta J.E. Gray, 1842. Designation of Patella caeca var. concentrica Middendorff, 1848 as a type of Cryptobranchia is invalid. For two species previously assigned to the genus Cryptobranchia [Lepeta concentrica (Middendorff, 1848) and Acmaea kuragiensis Yokoyama, 1920], the new generic name Cryptolepeta gen. nov. is proposed.

Three new species have been added to the formerly monotypic genus Liobaicalia Martens, 1876. We employed a combination of morphological, anatomical, and molecular approaches using mitochondrial COI gene, nuclear ATP-synthase alpha subunit gene intron (ATPase), and ITS1 spacer to delineate species boundaries between Liobaicalia stiedae (W. Dybowski, 1875), L. sidelevae sp. nov., L. karabanovi sp. nov., and L. riedeli sp. nov. The Liobaicalia species inhabit burrowing into sandy substrates in disparate regions of the ancient and/or recent deltas of the inflows to the south and central Baikal basins near tectonic faults where gases discharge happens. The genus Liobaicalia was not recovered as monophyletic based on current molecular-phylogenetic analyses based on mitochondrial COI data. We discussed discordance between morpho-anatomical and genetic traits, the possible origin of the Liobaicalia species, and the occurrence of scalariform shells in Baikal and non-Baikal gastropods belonging to different families.

Gastropod mollusk Jujubinus exasperatus is recorded for the first time in the Black Sea off the coast of Crimea. A brief species diagnosis, photographs of the shells and live specimen in situ are provided. Previously, the species was listed for the fauna of Russia and the Black Sea based on literary sources, the reliability of the information discussed in this paper. The possibility of naturalization of J. exasperatus in the Black Sea ecosystem is considered. J. exasperatus is recognized as an accidental element of the Black Sea benthos.

The taxonomic status of Indoartemon vietnamensis Thach, 2020 is reassessed. The morphology of I. vietnamensis falls within the intraspecific variation of I. huberi (Thach, 2016). The similarities suggest that I. vietnamensis should be treated as a junior subjective synonym of I. huberi. Furthermore, a new subspecies of the genus Indoartemon is described from Chua Chan Mountain, Dong Nai Province, Vietnam. Indoartemon huberi chuachanensis subsp. nov., has oblique-heliciform shell with axially deflected last whorl, narrow and deep umbilicus, aperture with one strong parietal lamella and one small palatal lamella, slightly enlarged columellar fold along the columellar margin.

The morphological features and ultrastructure of the hinge margin of the giant oyster Magallana gigas larvae, which were obtained from a nursery with the Black Sea broodstock and grown under optimal conditions, were studied. The paper presents scanning electron micrographs of disarticulated larval valves at different stages of development. In larvae at the D-veliger stage (2 days old, shell dimensions: 72×62 μm), as well as at the veliger stage (shell dimensions: 84×96 μm), the provinculum of the right and left valves consists of two anterior and two posterior teeth. We noted 2 to 3 teeth on the provinculum in both ”uneyed“ (H: 140–182 μm) and ”eyed“ velikonch larvae (H: 200–230 μm) on the anterior and posterior edges of the right and left valves. In pediveligers (H: 338–358 μm) there are two anterior teeth in the hinge margin of the right and left valves; the posterior teeth are reduced. We also determined logarithmic dependences of the hinge margin length (l, μm) on the length (L, μm) of the shell [l=32.518•ln(L) – 96.35; R2=0.904] and the maximum provinculum width on the shell height [c=5.8937•ln(H) – 17.994; R2=0.8993] of larvae ranging in size from 72×62 to 322×358 μm. The morphological characteristics and provinculum ultrastructure of the reared larvae were compared with those of M. gigas larvae of Atlantic and Pacific origin. The article discusses the potential hybrid nature of the Black Sea broodstock.