New subterranean freshwater gastropods of Montenegro (Mollusca: Gastropoda: Hydrobiidae), with description of one new genus and two new species

Two new stygobiont species of the family Hydrobiidae Troschel, 1857, i.e. Iverakia hausdorfi n. gen. n. sp. and Bythiospeum demattiai n. sp. were described. The both species have been collected from the spring Iverak near Podgorica. Descriptions and photos of the holotypes are presented.


Introduction
To date, 28 hydrobiid species and subspecies belonging to 10 genera have been recorded in Montenegro . Some of hydrobiid gastropods are stygobiote species, i.e. living in underground waters. The list of subteranean species of hydrobiiod gastropods of Montenegro (see: Glöer 2012, Glöer and includes 12 species from 7 genera: Bracenica Radoman 1973 (B. spiridoni), Saxurinator Schütt 1960 (S. orthodoxus), Vinodolia Radoman, 1973 (V. matjasici, V. gluhodolica), Montenegrospeum Pešić & Glöer 2013 (M. bogici), Zeteana Pešić & Glöer 2014(Z. ljiljanae), Paladilhiopsis Pavlovic 1913(P. tarae), and Plagigeyeria Tomlin 1930. Most of these stygobiote species rarely been sampled in subterranean habitats and only being recorded on the basis of empty shells in springs which flow directly out of the ground. Shell morphology is sometimes the only way to describe such stygobiotic snail species, because there is no any possibility for sampling living populations in the underground and study the anatomy of these gastropods (De Mattia 2007, Georgiev 2013. Recently, the junior author collected in a spring near Podgorica hydrobiid snails which did not correspond to any described species. Unfortunately, we did not manage to find living specimens (despite the continued effort of sampling almost every month over the year) of the new species. Descriptions of these species are given in this paper.

Material and Methods
The specimens of new species, were collected from April to mid-November 2014, in the spring Iverak situated in the village Pričelje (42°30'17.52'' N, 19°13'17.93'' E) in the central part of Montenegro. The

Research Article
spring is located roughly 150 m of the Zeta river. In order to collect live specimens, the spring sediments were transported into the laboratory, soaked in tap water and left in the dark for a few days in order to leave enough time for live animals to reach the surface of the sediment. In these samples two new species have been found but only with empty shells.
Photos of the shells were taken with a Leica digital camera system. The studied material is stored in the Zoological Museum of Hamburg (ZMH). Diagnosis. Shell elongated conical with a smooth surface. Aperture oval, from lateral view sinuated, the lower part moved forward. Anatomy is unknown.
Etymology. Named after the spring where the new genus was detected.
Differentiating features. The new genus share elongated shell with a sinuated aperture with Plagigeyeria Tomlin, 1930 and Paladilhiopsis Pavlović 1913. The both genera can easily be distinguished by the shell surface which is in Plagigeyeria ribbed, with a strong axial sculpture, and in Paladilhiopsis with a spiral lines on the shell crossing the growth striae (Bernasconi 1990), not smooth as in Iverakia n. gen.
The similar genus Zeteana Glöer & Pešić 2014, described from the same type locality as Iverakia n. gen., conchologically resembles to snails of the new genus but clearly differs by having the slightly ribbed shell surface, with broad ribs and thin interspaces  Etymology. Named after Prof dr Bernhard Hausdorf, curator of ZMH, in appreciation of his contribution to the taxonomy of the molluscs.

Description
Shell: Shell elongated cylindrical with a large and obtuse apex (Fig. 2). The regularly growing 5.5 whorls are slightly convex with a deep suture. Shell surface smooth. The aperture is ovoid, the lower edge of the aperture is moved forwards, and the outer margin is sinuated from the lateral view (Fig. 3). The umbilicus is open and deep. The shell height 2.4 mm, shell width 1.0 mm, apertural/shell height ratio 0.3.
Soft body: unknown.

Distribution.
Montenegro; known only from the type locality. Bythiospeum demattiai n. sp. (Fig. 4-6 Etymology. Named after Willy De Mattia (Trieste) in appreciation of his contribution to the taxonomy of the molluscs.

Description
Shell: Shell elongated cylindrical with a large and obtuse apex . The regularly growing 4.5 whorls are convex with a deep suture. Shell surface smooth. The aperture is ovoid, the outer margin is straight from lateral view (Fig. 6). The umbilicus is closed. The shell height 1.3-1.7 mm, shell width 0.7 mm, apertural/shell height ratio 0.3.
Soft body: unknown. Differentiating features. The specimens from the Iverak spring are tentaively ascertained to the genus Bythiospeum Bourguignat, 1882. However, considering that most of the numerous nominal species of Bythiospeum recorded from Europe are known as empty shells (Haase 1995) only one could expect that phylogenetic relationships within this group (including Paladilhiopsis Pavlović, 1913 as well) may be complex, and the genus is polyphyletic (Falniowski et al. 2014). Recently we described a new species of Bythiospeum Bourguignat, 1882 based on empty shells from Taban spring, situted only a few kilometres from the type locality of the new "Bythiospeum" species. Later on, we collected live specimens (Pešić and Glöer 2013), and ascribed B. bogici to a new distinct genus Montenegrospeum Pešić & Glöer, 2013, confirmed by molecular analysis (Falniowski et al. 2014). Montengrospeum bogici (Pešić & Glöer 2012) can easily be distinguished by the large dimensions of the shell (2.3 mm vs. 1.7 mm in B. demattiai) and having the circular, not ovoid, aperture. The shell of the new species resembles those of Devetakia Georgiev & Glöer, 2011 but the body whorl in the species of the latter genus known only from Bulgaria is more protruded (Georgiev and Glöer 2011).

Distribution.
Montenegro; known only from the type locality.