The syntypes of Carychium reticulatum Hauffen, 1856 and Carychium bidentatum Hauffen, 1856, thought to be lost to science, have been rediscovered in a recent inventory of the shell collection of Domink Bilimek (1813–1884) at the University of Natural Resources and Life Sciences in Vienna, Austria (BOKU). In this work, we present (1) the historical context of the Dominik Bilimek and Heinrich (also: Henrik) Hauffen collections and (2) provide a contemporary image dataset of Hauffen’s original material while considering today’s taxonomic understanding of the genus Zospeum. We clarify the taxonomic status of the syntypes by using light microscopy, Scanning Electron Microcopy (SEM) and 3D X-ray Micro-CT data in conjunction with Hauffen’s original illustrations and compare them to contemporary investigations of their closest congeners. Analysis of Zospeum reticulatum (Hauffen, 1856) is supported by historical documentation from Heinrich Hauffen’s original annotations and Bilimek’s diary entries, as well as from individual collection labels in Hauffen’s own script (verified by archive material from the Archive of the National Museum of Slovenia, NMS). Hauffen’s descriptions are based on apertural morphology and shell microstructure. Our re-investigation of Zospeum reticulatum provides corroborating evidence supporting its assignment to Zospeum spelaeum (Rossmaessler, 1839) while that of Carychium bidentatum corroborates its status as junior synonym of Zospeum costatum (Freyer, 1855).

Cave snails, history of sciences, natural history collections, type specimens

The importance of original type specimens is unquestionable for taxonomic evaluations and for upholding the international standards of reference that provide objectivity in zoological nomenclature (ICZN 1999). There are many incidences where original specimens were not preserved, became lost (Inäbnit et al. 2019), or got destroyed in the ravages of war (Janssen 2006). However, sometimes valuable material reappears serendipitously during inventories of other collections (Albano and De Mattia 2010; Salvador et al. 2023). We present a case in point, whereby the syntypes of Carychium reticulatum Hauffen, 1856 and Carychium bidentatum Hauffen, 1856, of the troglobitic genus, Zospeum Bourguignat, 1856, from Heinrich Hauffen’s original collection, considered lost, reappeared in the natural science collection of Dominik Bilimek, housed at the University of Natural Resources and Life Sciences in Vienna, Austria (BOKU). In this paper, we present the historical context of the Bilimek and Hauffen collections (for biographic information see also Lukeneder et al. 2023) and provide a contemporary image dataset of Hauffen’s original material considering today’s taxonomic understanding of the genus Zospeum. We assess the species using light microscopy, SEM and X-ray Microcomputer-Tomography (X-ray Micro-CT) data. Current geographical information regarding older cave names is provided.

Zospeum reticulatum is considered a junior synonym of Zospeum spelaeum (Rossmaessler, 1838) in the most recent work of Inäbnit et al. (2019). Historically, Zospeum spelaeum is a much-debated species showing a wide spectrum in representation of shell characters, from smooth shells to ribbed shells to those that are highly reticulated and bidentate or tridentate (Frauenfeld 1856; Hauffen 1856a). Although Hauffen (1856b) found his shells very similar to those of C. schmidtii (Frauenfeld, 1854), he and Von Frauenfeld (1856) debated over the taxonomic significance of the number and position of denticles and the density of reticulate microstructure on the teleoconch as unique, diagnostic characters. Meanwhile, contemporary methods of analysis have enabled major access into the shells of these microscopic snails, not possible in 1856. These have revealed new image data providing evidence of the taxonomic significance of signatory structures such as the shape and form of the columellar apparatus, the form of the lamella and the alignment and configuration of the umbilical zone (Inäbnit et al. 2019; Jochum et al. 2024).

In this present work, and in the absence of supporting DNA sequence data from these populations, we delve into Hauffen’s and Frauenfeld’s morphological quandary by re-investigating this recovered material via new image data while cross checking the potential taxonomic significance of the initial species designation (i.e., C. reticulatum versus Frauenfeld’s C. schmidtii and Freyer’s Z. costatum). Consequences ultimately would affect species status and taxonomic assignment within Zospeum.

The six syntype lots from the Bilimek Collection - catalogued at the BOKU - are listed in chronological order by their collection registration number in Table 1. The specimens are imaged and discussed in more detail below. Information about their synonymy and chresonymy is provided.

Systematic section

Genus Zospeum Bourguignat, 1856

 Zospeum spelaeum (Rossmaessler, 1839)

Figs 2, 3, 4

Carychium spelaeum Rossmaessler, 1839, Icon., (1) 2 (1/2): 36–37, pl. 49 fig. 661 (shell) [in der Adelsberger Höhle in Krain an Stalaktiten (Postojnska jama, near Postojna)].

Carychium reticulatum Hauffen, 1856, Verh. zool.-bot. Ges. Wien, Abh., 6: 623–624, pl. 7 fig. 4 (shell) [In der Grotte Bidou sturm (Hauffen leg.; Dobruška jama, near Vodice)].

Zospeum spelaeum: twelve junior synonyms are attributed to Z. spelaeum (see Inäbnit et al. 2019).

Material examined

Carychium reticulatum Hauffen: imaged syntype BOKU F3434b, other syntypes BOKU F3434a, BOKU F3434j, Cave Bidou sturm [= Dobruška jama], coll. Bilimek ex Hauffen 1856.

Figure 2. 

Light microscopic images of Hauffen’s specimens of Carychium reticulatum var. bidentatum Hauffen, 1856 (syn. Z. spelaeum Rossmaessler, 1839) BOKU F3434 from the type locality cave, Bidou sturm in Slovenia A–D Shell specimen BOKU F3434b in apertural view (A), dorsal view (B), apical view (C), umbilical view (D) E–H shell specimen BOKU F3434a in apertural view (E), dorsal view (F), apical view (G), umbilical view (H) I–L Shell specimen BOKU F3434j in apertural view (I), dorsal view (J), apical view (K), umbilical view (L). Scale bars: 1 mm.

Diagnosis

(Hauffen original from German). “Distinct vertical and horizontal lines form an entirely complete network pattern unique to this species”.

Figure 3. 

Hauffen’s specimens of Carychium reticulatum Hauffen, 1856 from the type locality, Bidou sturm in Slovenia. Inventory number BOKU F3434 A–G 3D visualizations of Micro-CT data of specimen BOKU F3434b showing the columellar apparatus; apertural view (A, E), dorsal view (B, F), apical view (C), umbilical view (D), lateral view (G) H–J scanning Electron Microscopy images of shell F 3434j (apical view) I detail of H showing protoconch J reticulated sculpture of Zospeum reticulatum Hauffen, 1856 K broken shell of specimen BOKU F3434d in dorsal view exhibiting collumellar apparatus L collection label of BOKU F3434. Scale bars: 1 mm (A, B, C, D, E, F, G); 100 µm (H, I, J); 1 cm (L).

Description

(Hauffen original from German). “Shell with 6 whorls, the last is relatively large; suture moderate; shell glassy and transparent; the sculpture is ribbed with the ribs largest by the suture, between these are often smaller ribs which extend to the middle of the whorl, the long ribs begin in most cases at the third whorl and continue over the cross ribs; near the suture they are closer to each other, in the middle of the whorl [zone of greatest convexity] they are however further apart, these crossed over ribs form a network, hence the name; umbilicus somewhat open at the beginning, however closing rapidly, aperture elongate, peristome rim bent backwards, lipped, dented in on the right side; columella somewhat swollen, on which a small denticle is in the middle, which lies deeper inside the aperture, on the inner parietal side are two denticles, the one nearest the columella is the larger and begins closest to the opening, it is next to the smaller one, which lies deeper in the aperture, bending to the right, this smaller interior denticle is visible in some shells and barely visible in others, the parietal shield shows tiny pitting. Height 2.0–2.2 mm. Width 1.5 mm.”

Figure 4. 

Hauffen’s specimens of Carychium” reticulatum var. bidentatum Hauffen, 1856 (syn. Z. spelaeum Rossmaessler, 1839) from Glaven verh (Slovenia) and from Douga jama cave (Slovenia) A, B light microscopic images of broken shell BOKU F3473a from Glaven verh showing apertural view (A), apical view (B) C collection label of broken shell BOKU F3473a D–K specimens of BOKU F3429 from Douga jama (Slovenia) D, E light microscopic images of specimen BOKU F3429a showing apertural view (D), dorsal view (E) F–K 3D visualizations of Micro-CT data of specimen BOKU F3429b; apertural view (F), apertural view showing columellar apparatus (G), dorsal view showing columellar apparatus (H), lateral view (I), apical view (J), umbilical view (K) L, M scanning Electron Microscopy images of shell of BOKU F3473a from Glaven verh (L apical view M detail of reticulate microstructure on teleoconch) N collection label of BOKU F3429 with notation referring to Douga jama locality. Scale bars: 1 mm (A, B, D, E, F, G, H, I, J, K); 100 µm (L, M); 1 cm (C, N).

Measurements

(BOKU F3434b from Bidou sturm): sh = 2.14 mm; sw = 1.26 mm; ah = 1.01 mm; aw = 0.84 mm; hlw = 1.43 mm; SA = 58.55 deg.

BOKU F3429 from Douga jama: sh = 1.96 mm, sw = 1.18 mm; ah = 0.94 mm; aw = 0.78; hlw = 1.29; SA = 59.90 deg.

Distribution

(Hauffen Z. spelaeum). Caves Bidou sturm (= Dobruška jama) and Douga jama.

Remarks

Hauffen also recorded this species from a cave behind Laak. Re-investigation of his specimens from that cave herein (Fig. 5) revealed that they are not conspecific with Z. spelaeum from Bidou sturm (Figs 2, 3) but rather, with the species Z. costatum (Freyer, 1855) (see Inäbnit et al. 2019, fig. 5, C1–3).

Figure 5. 

Hauffen’s specimens of Zospeum costatum (Freyer, 1855) from Laak in Slovenia. Inventory number BOKU F3444 A–D shell specimen F3444b in apertural view (A), dorsal view (B), apical view (C), umbilical view (D) E–G 3D visualizations of Micro-CT data of shell specimen BOKU F3444a showing the columellar apparatus. Apertural view (E), dorsal view (F), lateral view (G) H, I scanning Electron Microscopy images of shell specimen BOKU F3444b (apical view) J–M shell specimen F3444d in apertural view (J), dorsal view (K), apical view (L), umbilical view (M) N collection label of BOKU F3444 with characteristic handwriting of Heinrich Hauffen. Scale bars: 1 mm (A, B, C, D, E, F, G, J, K, L, M); 100 µm (H, I); 1 cm (N).

Enhanced description of Z. spelaeum based on integrative taxonomic analyses of Inäbnit et al. (2019) and Micro-CT and SEM Data in this work

Diagnosis. Shell ca. 1.96 mm, transparent, elongate, or elongate-conical with an auriform and more or less thickened peristome, bearing two to three apertural barriers; columella with a single lamella.

Description. Shell conical, often more slender than other species, translucent when fresh; whorl never well rounded [as, for example, in Zospeum frauenfeldii (Freyer, 1855)], usually ovate-conic in form; shell surface usually ribbed, but variable, which has been used to differentiate subspecies in the past (present on the whole whorl as in “Z. s. costatum”, present on the upper part of the whorl as in (Z. s. schmidtii (fig. 4f–n) or completely absent as in (Z. s. spelaeum) (fig. 4a–e) (Inäbnit et al. 2019)), but the spectrum of variation within populations is too broad to establish congruence here; aperture taller than wide, the palatal side usually shouldered; the parietal shield well- differentiated from the lip, its shape either convex or straight; parietalis well-developed in the aperture, extending one whorl into the shell; columellaris visible in the aperture, in some cases disappearing within half a whorl into the shell or continuously weakening; a more or less oblique lamella is present above the middle of the short columella; a basal bulge is present just above the umbilicus; angularis in most cases present as a tooth of variable prominence; palatalis usually present. Protoconch covered with pits; interconnected pits on top of the protoconch densely aggregated into rows; pits on the side of the whorl distributed more randomly. Details of the radula and the Z. spelaeum clade within the most recent phylogeny of Zospeum are available in Inäbnit et al. (2019).

The Z. spelaeum shells herein (BOKU F3434b and BOKU F3429) show a well-formed oblique lamella on a centrally aligned columella, the base of the columella shows a basal, lamella-like bulge in dorsal and aperture facing right views (Figs 3F–G, 4H), forming the more or less pronounced columellaris, which ends deep in the shell and is visible behind the peristome on the columellar side (Figs 3A, E, 4D, F); the robust and well-developed parietalis extends one whorl into the shell, tightly exiting the columellar side of the peristome far up on the parietal shield, ending either before or up to its outermost edge (Fig. 3A, D); umbilical depression deep; columellar side of peristome arches over and oblique to umbilical depression on ventral side (Figs 3D, 4K), alignment of last ¼ whorl not compact. Central part of protoconch partially covered with interconnecting pits and singular pits aggregated in rows (Figs 3I, 4L); onset of ribbing begins at suture of second or third whorl and with increased reticulation of the third whorl some distance from the suture. More or less enhanced reticulation begins at the fourth whorl (Fig. 3H).

Considering the 148 specimens investigated in Inäbnit et al. (2019) and those of this study, Zospeum spelaeum differs from Z. costatum by a less expanded upper section of the palatal side of the aperture; from Z. lamellatum Bole, 1974 by its greatly reduced external ribbing and number and size of lamellae and apertural barriers; from Z. lautum (Frauenfeld, 1854) by its usually more slender shell, the presence of ribs, and its bearing a simple inclined lamella versus the more elaborate 3-tiered lamellar configuration in Z. lautum; from Z. trebicianum Stossich, 1899 by its larger size.

Distribution. Z. spelaeum is known from the region of Ljubljana, Slovenia westwards to the Brenta River in Italy, the region of Trieste, Italy, the island of Cres, and eastwards where the Sava River enters the Julian Alps and from the Vrlovka cave in the northeastern part of Croatia (see also De Mattia 2003).

 Zospeum costatum (Freyer, 1855)

Fig. 5

Carychium costatum Freyer, 1855, Sitzungsber. mathem.- naturw. Cl. kais. Akad. Wiss. Wien, 15 (1): 20, pl. [1] fig. 5a–c (shell) [Von Herrn Ferd. Schmidt in der Grotte bei Goričane unweit des fürstbischöflichen Schlosses Görtschach entdeckt (Babja Luknia, near Goričane)].

Carychium bidentatum Hauffen, 1856, Verh. zool.-bot. Ges. Wien, Abh., 6: 701, pl. 7 fig. 5 (shell) [„in der Grotte am Glaven vrh“ (Hauffen leg., 17 exx.)] (Hauffen 1856b).

Material examined

Carychium bidentatum Hauffen: imaged syntypes BOKU F3444a (Grotte hinter Laak), BOKU 3473a (Glaven vrh); other syntypes BOKU F3444b, BOKU F3444d, Cave behind Laak, coll. Bilimek ex Hauffen 1856.

Diagnosis

(Freyer, original from German). Vertically ribbed, bidentate carychid.

Description

(Freyer, original from German). Shell white, spired, overlayed with strongly pronounced vertical ribs. Those of the first four graded whorls are weaker, those of the sixth whorl do not reach the ventral side, hence the ventral side [umbilical zone] (fig. c) is smooth before the aperture; about 1/3 the distance beyond the peristome, five ribs extend from the umbilicus nearly fusing together with some obliquely oncoming ribs from the upper part of the whorl as shown in Fig. 5C. The peristome is flatly bent back, the palatal lip is dented, the left columellar side sinks straight down, flattening at the rounded basal part of the aperture. Aperture shaped like a gourd. The ridge-like denticle nearest the columella [columellaris] reaches to the leftmost side of the parietal shield; the second, shorter ridge-like denticle [parietalis] extends from the parietal side and lies directly across from the shouldered edge of the right apertural lip. Height 2 1/8 mm, Width 1 1/3 mm.

Measurements

(BOKU F3444 from “Grotte hinter Laak”, Slovenia): sh = 2.14 mm; sw = 1.09 mm; ah = 0.86 mm; aw = 0.67 mm; hlw = 1.17 mm; SA = 59.08 deg.

Distribution

(Hauffen Z. costatum) Cave behind Laak, Slovenia.

Enhanced description of Z. costatum based on integrative taxonomic analyses of Inäbnit et al. (2019) and Micro-CT and SEM Data in this work

Diagnosis. Shell ca. 2 mm, transparent, ribbed, with weak spiral lines, elongate-conical with an auriform and more or less thickened peristome, bearing four apertural barriers, two of which continue on the columella as lamellae.

Description. Shell conical, translucent when fresh; whorls somewhat shouldered, usually stronger than in Z. spelaeum; pronounced, equidistantly-spaced axial ribs present on each whorl, though not always covering an entire whorl; weak spiral striae are usually visible; aperture taller than wide, the upper half of the palatal rim shouldered and expanded; the parietal shield well differentiated from lip, its margin more curved than straight; parietalis well developed in the aperture, extending one whorl into the shell; columellaris visible in aperture, extending 3⁄4 of a whorl into the shell; palatalis always present; angularis sometimes present. Internally, the base of the columella continually widens from below the point of attachment of the short, oblique lamella, forming a robust base above the umbilicus (Fig. 5E). The low columellaris increases structural form as it swells up towards the base of the columella (aperture facing right) (Fig. 5G), reaching its fullest size at half-way its distance on the columella (dorsal perspective) (Fig. 5F). Visible also in NHMW-MOL-71847 from Babja luknja, Goričane (fig. 5c1–3) (Inäbnit et al. 2019).

The Z. costatum shells (BOKU F3444a and BOKU 3473a) show the same lamella to columellar configuration as that seen in NHMW-MOL-71847 (Inäbnit et al. 2019) as well as the mode and degree of smoothness versus interconnected ribbing described by Freyer (1855) on the body whorl and the ventral side (Fig. 5J–K, M).

Considering the 10 specimens investigated in Inäbnit et al. (2019) and the two individuals in this study, Z. costatum differs from Z. spelaeum by the generally more expanded shoulder of the upper palatal rim (not visible in the broken shell of BOKU 3473a from Glaven vrh) and the swollen, wider basal configuration of the columella; differs from Z. lamellatum by its smaller, single lamella and reduced dentition; differs from Z. lautum by the marked presence of ribs and presence of a single lamella; differs from Z. trebicianum by its enhanced degree of ribbing and larger size.

Conchological differences of considered morphological characters including fine or course ribbing, development or absence of spiral lines or the presence of a second parietalis, have long confounded taxonomists of the radially ribbed, zospeid morphs found in Dinaride caves and which were later lumped together under Zospeum spelaeum schmidtii (Frauenfeld, 1854) (Bole 1974). Later studies, based on comparative anatomical investigations (De Mattia 2005) and DNA sequence data (Inäbnit et al. 2019), rejected the subspecific dichotomy for Zospeum spelaeum (Rossmaessler 1839) in which the two species, Carychium bidentatum Hauffen 1856 and Carychium reticulatum var. bidentatum Hauffen 1856 became shuffled. All the while, type material of the two species could not be studied because it was considered lost until now. Though topotypic specimens of both species (Kuščer coll. Nrs. 437 and 10137 respectively) are known in the Ljudevit Kuščer collection in Trieste (MCSNTS) (De Mattia 2005), no other known Zospeum syntypes described by Heinrich Hauffen are preserved at the PMS, nor at the NHMW nor in the Freyer Collection housed at the MCSNTS (Inäbnit et al. 2019).

We remark that geographical names of towns and caves have changed through time via the historical reshuffling of geographical borders and languages such that there is no congruency, with today’s names and those before WWII. Complicating the situation further, Hauffen tended to interchange annotation of locality names. For example, the type locality of Z. reticulatum, Bidou sturm, was recorded by Hauffen in 1856. In 1858, he refers to this locality as Bidov šturm at the Dobrus Mountain. Later, in 1932, the same cave locality was recorded by Kuščer as Bidov šturm (De Mattia, 2005). According to the Cave registry of the Speleological Association of Slovenia (Kataster JZS), the original name is considered Dobruška jama (sin. Jama nad Dobrušo) 46,175061, 14,476235; altitude 399 m a.s.l. (pers. com. Rajko Slapnik, June 2023). On the other hand, the type locality of Z. bidentatum was considered by Hauffen to be from a cave in a gorge at the Glavni verh near Habach castle (also: Schloss Habbach; Grad Jablje; Slovenia) in one publication (Hauffen 1858b). This locality is also recorded by Hauffen as Glavni verh in his earlier documentation (Hauffen, 1858a) and spelled differently (also: Glaven vrh, Glaven verh, Glavni vrh; meaning “main peak”; “Hauptgipfel” in German) on his labels accompanying the Bilimek Collection material here. According to the Cave registry of the Speleological Society of Slovenia (pers. com. Rajko Slapnik, Sept. 2023) and Bole (1974), the cave, Jama pod Sp. Dobenim is synonymous with Glaven verh, where the speleologists Kuščer, Bole, and Velkovrh are recorded to have collected Zospeum shells (Bole 1974). Kuščer (1932) mentions a small cave, with limited access, just below the village Dobeno near Mengs. Jože (1977) identifies Glaven verh as kind of a flooded cave below Ručigaj (in Spodnji Dobene near Mengš) (Fig. 6).

Figure 6. 

The narrow entrance of Glaven verh identified as Ručigaj = Ručigajev izvir, is located in a small canyon as described by Hauffen (1858b). Photos: Matija Križnar, 2024.

Hauffen’s manuscript (Hauffen 1858b; Archiv NMS, leto 1856, št. 47) provides some further information about the characteristics of the small-scaled Glaven verh cave (Fig. 6), which should be located within a small canyon. The cave appears to be difficult to enter for ancient cavers (personal comm. Matija Križnar, 2024). The walls devoid of stalactites and the floor is covered with sand. A small stream should flow through the middle of the cave. Ručigaj corresponds to Ručigajev izvir, while “izvir” can be translated as “spring”. LiDAR (Light Detection and Ranging) photos confirm its position within a canyon.

Hauffen (1856a) loosely includes mention of the “Grottenschnecken” (= “cave snails”), Carychium lautum in “Glaven verh” and Z. alpestre (Freyer, 1855) in "Douga jama", which he also noted for harbouring C. reticulatum var. bidentatum in the same publication. Nevertheless, it is not clear if he actually sent this specific material, as stated therein to Frauenfeld, nor, if he later designated this material differently in his or another collection. We assume his notation referring to Glaven vrh all means the same cave by the Habach Castle (also known by 4 variable names, including Jablje Castle in Slovenian). Notable here, is that Inäbnit et al (2019) documents 3 shells (fig. 5d, NMBE 553383) from the nearby cave Jama 2 pri Jabljah (GPS: 46°08'30.9"N, 14°33'12.6"E) near Loka pri Mengšu (Laak bei Mannsburg). According to the Cave Registry of the Speleological Association of Slovenia, there is a very high density of caves within a very small radius in the region of Loka pri Mengšu of which Glaven verh (Ručigaj = Ručigajev izvir) is one.

By comparing our data to that of congeners in recent works (Inäbnit et al. 2019; Jochum et al. 2024), we reveal that the columellar apparatus of Hauffen’s broken syntype of C. reticulatum from Glaven verh and the syntypes from “Grotte hinter Laak” (Hauffen 1856b) match well with that of Zospeum costatum (Freyer, 1855) in Inäbnit et al. (2019) (fig. 5c1–3). On the other hand, the columellar apparatus, aperture shape, whorl and spire formation and the umbilical configuration of Hauffen’s C. reticulatum shells from Douga jama unequivocally match those within the spectrum of the species, Z. spelaeum (Rossmaessler 1839) in Inäbnit et al. (2019) (fig. 4b1–6). We emphasize that contemporary tools such as 3D X-ray Micro-CT and SEM imaging profoundly aid in the re-interpretation of former species designations while underscoring the significance of past evaluations in taxonomic investigations today.

The taxonomic examinations in this study therefore show that Hauffen’s syntypes correspond morphologically to those of known species namely, Zospeum spelaeum (BOKU F3434b and BOKU F3429) and Zospeum costatum (BOKU F3444 and 3473a). By comparing key zospeid diagnostic characters beyond size, surface structure and dentition, additional ones, such as internal coiling configuration of the columellar apparatus, lamella formation in relation to the columella, the degree and size of the umbilical depression in conjunction with the formation of the final coiling in the umbilical zone (ventral perspective) (Jochum et al. 2024), this work underscores the considerations of previous taxonomists, Frauenfeld (1856), Freyer (1855) and Bole (1974) (i.e. Z. spelaeum schmidtii) in its current taxonomic placement within the Z. spelaeum clade in Inäbnit et al. (2019).

This work documents Zospeum syntypes considered lost to science from the original collection of Heinrich Hauffen and which later landed in the Dominik Bilimek collection at the BOKU in Vienna, Austria. The absence of reliable type material precluded their fullest consideration in the documentation and interpretation of Z. costatum (Freyer, 1855) and Z. spelaeum (Rossmaessler, 1839) in the most recent integrative taxonomic examinations of the genus Zospeum (Inäbnit et al. 2019). Our contemporary morphological analysis of C. reticulatum using light microscopy, SEM and X-ray Micro-CT data in conjunction with Hauffen’s original documents and figures, illustrates the manifestation and degree of phenotypic variation on the shells (BOKU F3434b and BOKU F3429) of two populations of Zospeum spelaeum. Though we know little about the ecology of the respective caves, cave systems in the region of Loka pri Mengšu are densely represented, with many being contiguous and thus, sharing subterranean drainage systems. Zospeum snails get washed through these systems during seasonal water flows and displacement of fauna within a concentrated system of caves is not unusual (Culver and Pipan 2009). Considering that Z. s. schmidtii was reported from many caves in the region and in several cases sympatrically with Z. costatum (Bole, 1974), the potentiality of mixing of populations is high. Reticulated microstructure of the teleoconch is also known in other species such as Z. frauenfeldii (Freyer, 1855) and Z. costatum (Freyer, 1855). We confirm that although the reticulated microstructure of Hauffen’s specimens of C. reticulatum is more pronounced than in most other forms of Z. spelaeum of which it is considered a junior synonym, the shells (BOKU F3434b and BOKU F3429), and those of other former congeners such as the more or less reticulated variant, Z. s. schmidtii (see Bole 1974; Inäbnit et al. 2019), are otherwise, not differentiated enough to assign species status based on this character alone. We confirm that C. reticulatum Hauffen 1856 lies within the spectrum of character states taxonomically recognized for the species Z. spelaeum (Inäbnit et al. 2019). However, we remark that although this study considers the reticulated shells from the caves Bidou šturm and Douga jama to represent a phenotypic variation within the morphological spectrum known for Z. spelaeum, DNA sequence data from new material collected in these caves (and those of geographically proximal caves), would ultimately further our understanding of the Z. spelaeum clade. Since we do not rule out the potentiality that Hauffen‘s C. reticulatum populations might represent genetically separated evolutionary lineages of Z. spelaeum (i.e. having distinct DNA barcodes and nuclear DNA) (Weigand et al. 2014), this work especially opens new perspectives for future exploration and molecular investigations. Hence, we strongly encourage further speleological exploration and specimen collection in Bidou šturm (= Dobruška jama) as well as in Hauffen’s listed cave localities (Table 1). Lastly, we emphasize that this study demonstrates the long-term scientific value and significance of the preservation and maintenance of historical, natural science collections.

We gratefully acknowledge the following contributions: Father Meinrad Tomann and Father Alkuin Schachenmayr (both Heiligenkreuz) for supporting this work with historical material from the archive; Gabriela Gelovizza (Trieste) for sending a high-resolution scan of a Bilimek photograph; Jürgen Kriwet (Vienna) for providing infrastructure for photography at the Department of Palaeontology (Vienna); Jan Steger (Vienna) for support with Scanning Electron Microscopy (SEM); Matija Križnar (Ljubljana) for photos and information on the Glaven vrh cave; Alexander Lukeneder (Vienna) is thanked for support with photography at the NHMW; Rajko Slapnik for his help in providing details from the Cave registry of the Speleological Association of Slovenia (Kataster JZS).

We thank the editor Alexander Weigand and two anonymous reviewers for their helpful comments and suggestions. Many thanks go to the Austrian Academy of Sciences (ÖAW) for financial support of this project. AJ received support from the SYNTHESYS Project (financed by the European Community Research Infrastructure Action under the FP7 “Capacities” Program; pro­ject grant AT-TAF-5370). Open access funding provided by University of Vienna.