Volume 29

Vietnam with its limestone ranges that are concentrated mainly in northern, north–central and southern parts, and many different limestone islands running along the coastline, has a phylogenetically-diverse land snails fauna dominated by endemic species. The genus Cyclophorus (Cyclophoridae) in Vietnam is studied. Sixty species and subspecies from various habitats of limestone areas throughout Vietnam are confirmed and recorded. New species and subspecies, Cyclophorus implicatus kanhoensis ssp. nov., from Northwestern Vietnam, and Cyclophorus tamdaoensis sp. nov., from Northern Vietnam are described and discussed. In this paper, the Cyclophorus courbeti var. leucostoma Dautzenberg et Fischer, 1905, is elevated to subspecies.

Unio mongolicus Middendorff, 1851 (Bivalvia: Unionidae) was described from Gorbitza mountain stream (in the east of Trans-Baikal Territory, Russia) and the taxonomy has changed over the past century and a half. A specimen of Middendorffinaia mongolica from the Gorbitza stream collected 160 years later is a match with the type illustration of Unio mongolicus from the type locality. Comparison of the shell morphology of the type specimen of U. mongolicus with the modern specimen collected from this location, combined with our analyses of molecular, anatomical and conchological data of M. cf. mongolica species from rivers of the Upper Amur River Basin and the far eastern Russia, revealed that these taxa all belong to a single polymorphic species. The molecular analysis of the COI gene fragment mtDNA of examined Comparatory Species assigned to Middendorffinaia Moskvicheva and Starobogatov, 1973 confirmed they are only intraspecific forms of M. mongolica. Morphological and genetic distances between M. mongolica and Nodularia douglasiae Griffith et Pidgeon, 1833 confirmed their assignment to two independent genera. Differences of morphologically similar species M. mongolica, N. douglasiae and Unio crassus Philipsson in Retzius, 1788 were separated based on conchological characteristics and anatomical features. History of the taxonomic changes for Unio mongolicus is discussed here.

For the first time, the widely spread Antarctic species Leptochiton antarcticus was found at the Emperor Seamounts in the North Pacific Ocean. In spite of a large distance between the Emperor Seamounts and Antarctica, the found specimen have very similar shell, girdle, radula and gill features to the type material. I propose that L. antarcticus spread to the North Pacific from the Antarctic via a deep-water current near the ocean floor, and perhaps it inhabits the slopes of islands and continents from the South Ocean to the Emperor Seamounts.

Two substitution names are proposed for primary homonyms introduced for land snail of the family Camaenidae in Thach [2018].

The genus-group taxon Elbasania Schileyko et Fehér, 2017 has recently been introduced as a subgenus of Metafruticicola Ihering, 1892 for a species occurring in north-western Greece and Albania. Using mitochondrial and nuclear markers, the phylogenetic relationships of Elbasania within Metafruticicolini (Hygromiidae) are reconstructed. The results of these analyses suggest that Elbasania is more closely related to Hiltrudia Nordsieck, 1993, which has a range adjacent to that of Elbasania from Croatia to northern Albania, than to Metafruticicola. Elbasania shares with Hiltrudia and also Cyrnotheba Germain, 1929 a very characteristic microsculpture of the shell and an overall similar genital system, which however differs among these three taxa with regard to its internal structures, especially those of the penis. Therefore, it is suggested regarding Elbasania as a distinct genus here.

The predatory family Streptaxidae is comprised of five species occurring in Thua Thien Hue Province, central Vietnam. The present paper provides an assessment of the literature data relevant to these species and the description of two new species. Haploptychius bachmaensis sp. nov. has an oblique-heliciform shell with elevated spire. The aperture is subcircular, peristome discontinuous, thick and slightly expanded, apertural dentition with one strong parietal lamella. Perrottetia namdongensis sp. nov. has a rounded and protruded shell periphery. The aperture is subcircular, peristome is discontinuous, thick and expanded, apertural dentition with one large, strong parietal lamella, one small upper palatal lamella, one large palatal lamella, one large basal lamella, and one large strong columellar lamella.

All available data and most of materials on Acicula parcelineata from Ukraine are reviewed. Thirteen areas inhabited by the species are reported for Ukraine, some of which include several known sites. Five of these areas were not reported before. Map of general distribution of A. parcelineata is provided (outside Ukraine based on published data). Habitat preferences of this species are reviewed, it occurs in Ukraine almost exclusively in forests with presence of beech, on altitude 300-1100 m. Conservation status of A. parcelineata in Ukraine is shown to be “Near Threatened” according to IUCN criterions, it is recommended to be included into the next edition of Red Book of Ukraine. Shells’ measurements of A. parcelineata are provided and compared with related Platyla jankowskiana. The later species is discussed; it seems to be possible that it represents large abnormal specimens of A. parcelineata.

In present paper, we report the first findings of two large and conspicuous nudibranch species for Russian waters - Goniodoris nodosa and Flabellina pellucida. Both species show wide distribution in the northeastern Atlantic waters or even in the northwestern Atlantic in the case of F. pellucida. The morphology of both species was studied using anatomical dissections and scanning electron microscopy. Molecular diversity was assessed by sequencing of COI marker and reconstruction of haplotype networks. In the Barents Sea, both species show minor genetic differences from their European relatives and similar morphological characters. Putative explanations of new findings for Russian Arctic are discussed.

Anatomical study of five specimens of an endemic species of the Mauritius Island, Erepta odontina (Morelet 1851) showed that within one population disappearing of additional organs of the reproductive tract (epiphallic caecum, penial caecum, penial appendix, flagellum and retractor of penis) occur in four different combinations. It is significant that the shells of all five specimens were practically identical. It is assumed that the described phenomenon has a mutagenic nature and is regarded as a rare (if not unique) case of reduction (up to complete disappearance) of additional organs within one population.

It is proposed to restore the old name of the genus Terenochiton for Leptochiton norfolcensis (Hedley et Hull, 1912). We also provide a new description for the genus since the old description does not reflect the main features associated with the development of the articulamentum. All valves of the genus have rudimentary unslitted insertion plates. Similar rudimentary insertion plates have evolved independently in different families of the primitive chitons.