﻿Land snail diversity in central China: revision of Laeocathaica Möllendorff, 1899 (Gastropoda, Camaenidae), with descriptions of seven new species

﻿Abstract Central China harbors the native dart-sac-bearing camaenids Laeocathaica. The genus is revised and seven new species are proposed based on museum material and newly collected specimens. This work confirmed that most Laeocathaica species have restricted habitats. The comparison of the dart sac apparatus among the dart-sac-bearing camaenid genera indicated the importance of the presence of the proximal accessory sac that might be analogous to the membranous/muscular sac surrounding the proximal dart sac and/or the distal region of the vagina near the atrium, which also plays a significant role in the diagnosis of Laeocathaica species based on its number, symmetry and position on the dart sac. Species with similar shell morphology were studied using geometric morphometric methods to detect variations in shell shape. A molecular phylogenetic analysis based on 16S and ITS2 sequence data of partial Laeocathaica species and many other dart-sac-bearing taxa suggested that Laeocathaica might be monophyletic. Furthermore, the present phylogeny indicated that Stilpnodiscus, Cathaica, Bradybaena, and Pseudobuliminus might be polyphyletic and therefore the taxonomy of dart-sac-bearing camaenids in this region requires a thorough revision. This work reconfirms that the Southern Gansu Plateau is important as a hotspot for malacodiversity conservation on the Chinese mainland.


Introduction
Laeocathaica Möllendorff, 1899 comprises more than twenty species, most of which were described by O. von Möllendorff. It is a group of sinistrally-shelled camaenids indigenous to Central China, an area that includes western Hubei, Chongqing (administratively part of Sichuan before 1997), Sichuan, southern Gansu, and western Shaanxi (works before 1934 listed in References; Wu and Chen 1998;Chen and Zhang 2004;Páll-Gergely et al. 2022). This genus is characterized by a sinistral shell with a conic to strongly depressed spire, usually with a sharp carina, more or less reflexed aperture, broad umbilicus and weak or strong apertural barriers on the young shell. However, their shell morphological phenotypic variation is so wide that most shell characters can also be observed in other dart-sac-bearing camaenids of China, such as toothless and toothed aperture of juvenile/mature shell, rounded and carinate periphery, narrow and broad umbilicus, scaly and smooth periostracum, banded color pattern and so on, which makes us question, whether it is a monophyletic group (Páll-Gergely et al. 2022). It is noteworthy that in the original paper on the introduction of this genus Möllendorff (1899) noticed that this group might be distinguished from other related genera by "juniora labro interno munita", which means "during postembryogenesis several sets of teeth, different from those developed at adult stage in shape and/or number, present and remained to adult stage" (Schileyko 2004). In comparison to the shell characteristics, which are not always reliable taxonomic markers, the characteristics of genitalia are considered important to the systematics of dart-sac-bearing camaenids. Unfortunately, the genital anatomy of Laeocathaica species described so far has been insufficiently investigated, except for very few species (Wiegmann 1900;Schileyko 2004), whose absence makes the delimitation of the genus problematic.
This paper examines the shell morphology and genital anatomy of Laeocathaica using museum material and recent field collections and proposes seven new species. A molecular phylogeny based on 16S and ITS2 sequence data of a subset of Laeocathaica species and other dart-sac-bearing taxa is constructed to explore whether Laeocathaica is monophyletic.

Specimen preparation and observation
Animals in most cases were relaxed by drowning in water before being transferred to 70% ethanol for fixation, which was replaced with ethanol of the same concentration after 3 days. To observe the animals with evaginated dart sac apparatus, before fixation the animal was drowned in water with 5% ethanol, 10% ethanol and 15% ethanol, in each solution for ~ 60 min. Photographs for illustrations (by MW) and geometric morphometric analyses (by WS) were taken using a Canon camera. The shells were measured with digital vernier calipers to the nearest 0.1 mm. Whorls were counted following Kerney and Cameron (1979) to the nearest 0.125 (= 1 / 8 ) whorls. Shells were observed under a scanning electron microscope Sigma 500. The penis was dissected at the opposite side of penial retractor insertion. The dart sac was dissected by cutting the dorsal part of the dart sac (see Fig. 1A) along the line from the atrium to the dart sac chamber. Directions used in the general descriptions of genitalia: proximal = towards the genital atrium; distal = away from the genital atrium. For directions used in the description of dart sac apparatus, refer to Fig. 1. Illustrations of genitalia were drawn based on actual photos (by MW). The corresponding Chinese name for person, new species, or locality is present only once in square bracket when necessary.

Map preparation
Distribution maps were created using ArcGIS Desktop 10.8 under GCS_WGS_1984 coordinate system. In addition, mapping was carried out to map both the distribution limit and the distribution pattern of Laeocathaica species (Fig. 2A). The nearby places where Laeocathaica was not found, represented by the counties/cities where the field work was carried out at one or more sites, are as follows:   (Möllendorff in Ancey, 1889), L. hisanoi Páll-Gergely, 2022, and L. leucorhaphe Möllendorff, 1899 whose precise localities are not known; white dots: the localities where no Laeocathaica species was ever found B distribution of the new species described in this paper, yellow dots: L. qingchuanensis Wu, sp. nov., green dot: L. zhengpingliui Wu, sp. nov., brown dots: L. parapolytyla Wu, sp. nov., white dot: L. qiminglii Wu, sp. nov., pink dot: L. cheni Wu, sp. nov., blue dots: L. qishilii Wu, sp. nov., orange dots: L. nordsiecki Wu, sp. nov. C distribution of L. carinifera (H. Adams, 1870) (green dots), L. qingchuanensis Wu, sp. nov. (yellow dots), and L. stenochone Möllendorff, 1899 (blue dots) D distribution of L. amdoana Möllendorff, 1899 (green dots), L. distinguenda Möllendorff, 1899 (pink dots), and L. tropidorhaphe Möllendorff, 1899 [南川县]. It should be noted that the map ( Fig. 2A) is far from complete, as any survey carried out in such a vast area could normally have provided very limited information about its malacofauna, not to mention that these places comprise 91 counties/cities of seven provinces, covering an area of ~ 1,080,000 km 2 (calculated from Fig. 2A).

Geometric morphometric analyses
Geometric morphometric methods (GMM) were used to investigate the relationship between some species that exhibits conchological similarities. The morphological variation analyses of the shells were performed in the tps series software including tpsUtil32  Möllendorff, 1899 (white dots), L. phaeomphala Möllendorff, 1899 (blue dots), L. polytyla Möllendorff, 1899 (yellow dots), L. potanini Möllendorff, 1899 (red dots), and L. prionotropis Möllendorff, 1899 (orange dots). Range of the map is defined by the rectangle in the thumbnail. (Rohlf 2004), tpsDig32 (Rohlf 2005), and MorphoJ (Klingenberg 2011) using geometric morphometric methods based on the landmarks and semi-landmarks on the profile of the aperture-viewed shell (Schilthuizen et al. 2012;Wu et al. 2019a). The landmarks and semi-landmarks treated equally in the analyses were designed as follows: LM 1 , the crossing of peristome and right profile of body whorl; LM 2 , the columella insertion; LM 3 , the left insertion of peristome onto body whorl; LM 4 and LM 6 , the right and left terminal points on last suture, respectively; LM 5 , apex of shell; LM 7-24 , eighteen semi-landmarks on the peristome between LM 3 and LM 1 by length; LM 25-39 , fifteen semi-landmarks on the right profile between LM 1 and LM 4 by length (Fig. 1B).
Chromatographs and sequences were first studied and compiled in sequencer 4.5. DNA sequences of both genes were aligned by T-Coffee with standard parameters (Di Tommaso et al. 2011). Then the badly aligned parts (marked green and purple in T-Coffee, indicating inferior alignment) were deleted. For the subsequent analyses a concatenated matrix of 91 (incl. outgroup, table 1) × 1068 bp (incl. gaps) was used. The model selection was made using "Models" in MEGA 7.0.26 (Kumar et al. 2015). The dataset was analyzed by Bayesian Inference (BI) in MrBayes 3.2.4 (Ronquist et al. 2012). While the dataset was analyzed using the Maximum Likelihood Analysis in raxmlGUI 2.0 beta (Edler et al. 2019), applying the GTRGAMMA+I model and reps 1,000. Three independent runs were performed in Bayesian Inference Analysis, each of which was performed for 1,000,000 generations and sampled every 1,000 generations, where the first 25% samples were discarded as burn-in. The convergence of the Markov Chain Monte Carlo simulations was investigated with tracer v. 1.7 (Rambaut et al. 2018) to confirm that all ESS values exceeded 200. Helix pomatia Linnaeus, 1758 (Table 3) was used as an outgroup for rooting phylogenetic trees. New DNA sequences were deposited in the NCBI GenBank under the accession numbers ON261686-ON261865 (Table 3).

Supraspecific classification
The generic classification of species adopted in this study mainly follows MolluscaBase (2021a-p; 2022a-c) ( Table 3).

Comparative examination of the terminal genital organs in Laeocathaica
The most complicated structure in the genital system of dart-sac-bearing camaenid species (here, we use "dart-sac-bearing camaenids" to replace the former subfamily Bradybaeninae), if present, is the dart sac apparatus, a sack-like structure on the vagina. The basic structure of a dart sac apparatus consists of a dart sac, the muscular blind tube that contains and can secrete the love dart, the penis insertion/opening and the vagina insertion/opening. The ventral side of the dart sac usually has an accessory sac that is distally connected by mucous glands and opens into the chamber containing the love dart or opening into the dart sac chamber. The mucous glands consist of several mucous gland tubes that are simply branched (i.e., only one tube or bifurcate tube) or complicatedly branched and covered, packaged and connected by a sheet of loose connective tissue that binds the mucous glands more or less tightly to the vagina (Fig. 4B). The nerve fibers that connect the mucous gland tubes (e.g., Wu 2019: fig. 5C), together with the proximal nerve fibers that connect the dart sac (incl. accessory sac), fuse into a main nerve fiber that is attached to the surface of the proximal oviduct before it enters the body wall of the animal. Bilateral symmetry (for directions see Fig. 1A) of a dart sac apparatus consisting of the above components has been observed in many genera of Bradybaeninae (Wu 2004). However, the position of the membranous sac surrounding the partial dart sac and/or distal region of the vagina proximal to the atrium (DVM) makes the dart sac asymmetric in some genera, e.g., in Laeocathaica.
The DVM in dart-sac-bearing camaenid snails, has been ignored in many studies (e.g., those works before Wu and Guo 2003), or not particularly emphasized (e.g., in Stilpnodiscus entochilus Möllendorff, 1899, Wu (2004 fig. 16E): the sac around the space  Wu,sp. nov. (HBUMM08298spec.8,paratype), showing relative position of dart sac apparatus, vagina, and penis A evaginated pouch of terminal genitalia B the exposed pouch. Arrow indicates the position of the proximal accessory sac. Abbreviations: DS -dart sac; Dt -love dart; EDC -entrance of dart chamber; EOV -external opening of vagina; EOP -external opening of penis; MG -mucous glands; P -penis; PAS -proximal accessory sac; PO -opening of proximal accessory sac leading to dart sac chamber or dart chamber; Va -vagina. between V2 and V3), or treated by some authors as DVM (in Trichobradybaena ; in many species in Wu 2004; Wu 2019: table 1 for incomplete taxa,  see below), or with alternative nomenclature referring to structures which are close in position and/or shape and blind or open into the dart sac chamber (i.e., "finger-shaped structure" in Stilpnodiscus moellendorffi Wu, 2001; "bladder" in Laeocathaica polytyla in Schileyko (2004); "bridge-like structure" in Ponsadenia spp. in Wu and Guo (2006); "proximal accessory sac", in Traumatophora triscalpta (Martens, 1875) in Wu (2019) and in Pseudiberus spp. where both blind ones or those open into the dart sac chamber were observed in Zhang et al. (2021)). The opening of the DVM was not recorded prior to observation in T. triscalpta (Wu 2019). The so-called DVM structure cannot be distinguished from the proximal accessory sac in position, external morphology or internal structure. The fact that the conjunction of DVM structure and the proximal accessory sac was not observed in any Chinese bradybaenine genus (Wu 2019: table 1) suggests that they are originally the same organ. Consequently, in this work, the proximal accessory sac refers to "a membranous (or muscular) sac that partially surrounds the dart sac and/or distal region of the vagina proximal to the atrium" that does not differ from the DVM.
The proximal accessory sac, whose opening leads to the outside of the body (if is not blind) (Fig. 4), has been speculated to be the place where the fluid secreted by the mucous glands is stored (Zhang et al. 2021). Connecting with the chambers inside the dart sac apparatus, the PLS structure (e.g., in Aegista (Aegista) accrescens (Heude, 1882), Wu (2004: fig. 13C); Aegista (Plectotropis) gerlachi (E. Martens, 1881), Wu (2004: fig. 14B-D); in Metodontia houaiensis houaiensis (Crosse, 1882), Wu and Pro-zorova (2006: fig. 3C), has yet to be proven that it is a modified PAS. When the dart sac apparatus in Laeocathaica is evaginated outwards to the body wall prior to dart shooting and epiphallus protrusion, an external sac is formed exposing the penial, vaginal and dart sac orifices and the proximal accessory sac (Fig. 4). Functionally, the proximal accessory sac forms a "cushion" (Fig. 4, arrowed) filled with the fluid secreted by the mucous glands during the pre-copulatory behavior. The shape, size, and number of openings of the proximal accessory sac are believed to be related to the compatibility of courtship behavior, which affects the efficiency of copulation.
In Laeocathaica it is most commonly observed that two proximal accessory sacs, the left and the right, each with a pore leading to the dart chamber or dart sac chamber, are dorsally separated and ventrally fused. For Laeocathaica phaeomphala Möllendorff, 1899, L. polytyla Möllendorff, 1899, andL. tropidorhaphe, the dart sac has no proximal accessory sac (Figs 23,26,34). The only species that has one proximal accessory sac is Laeocathaica dolani   (Fig. 7). Two of the three species without proximal accessory sac have the elongated vagina part between atrium and dart sac (Figs 23A, 34A; Table 1). However, the third species Laeocathaica polytyla has neither a proximal accessory sac nor the elongated vagina part (Fig. 26). We can hardly guess how the love dart is to be exposed outside body through the long distance of the elongated vagina part, based on our knowledge of the normal situation of dart shooting in the genus, as showed in Fig. 4. The presence of two proximal accessory sacs in Laeocathaica amdoana, which has the relatively smallest proximal accessory sac in the genus (Fig. 6B, C), makes L. amdoana a species that may has a transitional state among the species that have large and ventrally fused proximal accessory sacs (e.g., in L. carinalis Chen & Zhang, 2004, Fig. 8), have large but ventrally separated proximal accessory sacs (e.g., in L. zhengpingliui Wu,sp. nov.,Fig. 38) and have no proximal accessory sac (e.g., in L. phaeomphala, Fig. 23).
Unlike the structurally closed proximal accessory sac observed only in Pseudiberus tectumsinense pingi Zhang & Wu, 2021, the proximal accessory sac observed in all Laeocathaica species has an opening/pore leading to the dart chamber (for most species) or dart sac chamber (for L. amdoana only) instead of the proximal accessory sac opening leading only to dart sac chamber as observed in Traumatophora Ancey, 1887 (Wu 2019) and in Pseudiberus Ancey, 1887 (Zhang et al. 2021). In Laeocathaica, the proximal accessory sac pore is located at the distal end of the proximal accessory sac, opening into the proximal dart chamber, or at the central part of the proximal accessory sac, opening into the dart sac chamber. Accordingly, if the dart sac is evaginated during the mating of the snail, the pore is exposed to the outer environment or not deep in the dart chamber (Fig. 4).
Description. Shell sinistral, strongly depressed to broadly conic, moderately solid, of 5-10.5 almost flat whorls. Last whorl abruptly descending in front, angulated to strongly keeled; rarely rounded. Coloration consists of whitish, corneous, or chestnut background and mostly with one or two dark sub-peripheral bands; besides, usually there are several fulvous, diffuse radial streaks. Protoconch usually with fine radial threads and/or fine granules that each is formed by a low hump deposited in a shallow socket. Sculpture of teleoconch whorls varying from fine, silky radial striation to rather strong ribbing; on basal surface below keel or angle this sculpture becomes much weaker. Aperture rounded to peach-shaped, oblique, margins usually more or less reflexed. Within aperture a ring-like thickening present. Apertural teeth absent or with one tuberculiform basal tooth and sometimes with another one on palatal wall. During postembryogenesis several sets of teeth, different from those developed at adult stage in shape and/or number, present and remained to adult stage. Umbilicus moderate to very wide, ratio of umbilicus diameter to maximum diameter 0.21-0.50. Height 3.5-14 mm, maximum diameter 10.0-29.5 mm.
On left and right side of mantle edge, no leaf-shaped appendage present. Head wart between ommatophores present, weak, or developed. Jaw arcuate, with 3-8 more or less projecting ribs.
Slender vas deferens entering epiphallus at penial retractor muscle insertion. Penis generally clavate, rarely subcylindrical. Penis internally divided into three regions: the proximal part with narrow or thick longitudinal pilasters, among which one pair or two pairs of adjacent pilasters fuse into one Y-shaped fork or two Y-shaped forks (not in Laeocathaica christinae, L. phaeomphala, and L. qingchuanensis Wu, sp. nov.). The median part, composed of fine pilasters that weave into network or covered by isolated tonguelike/diamond-like granules erecting on penial wall. The distal part, near epiphallic opening, with mini-pilasters crowded and forming several short and thick pilasters. Epiphallic papilla absent. Penial sheath always present, surrounding proximal penis. Dart sac always present. Accessory sac presents at ventral dart sac, internally solid or narrowly empty. Mucous glands 2-12, each simply or complicatedly branched, entering accessory sac separately before being united into a common duct inside wall of accessory sac. Proximal section of dart sac with 0-2 PAS that if present, each has a tiny opening leading to dart chamber. Vagina between atrium and dart sac elongated only in a few species. Bursa copulatrix duct subcylindrical throughout (modified from Schileyko 2004).
Remarks. Laeocathaica species are granulate on the protoconch, which is smooth in actual observation due to erosion or weathering. In the original description of Laeocathaica filippina, Heude (1882) first mentioned the irregular white radiate stripes (1882), which were particularly noted by Möllendorff (1899) as "die stets vorhandenen Jugendlippen (the ever-present juvenile lips)" that joined the definition of Laeocathaica. Möllendorff (1899) also noticed in Euhadra haplozona Möllendorff, 1899 and Euhadra eris Möllendorff, 1899 such "ever-present juvenile lips" exist. The juvenile lips, which have remained on the mature shell, may be frequent and weak such as those of L. minwui Páll-Gergely, 2022 (Fig. 11A) and many other species, or sparse and strong as those of Laeocathaica dityla (Fig. 13D) and L. parapolytyla Wu, sp. nov. (Fig. 25). Regarding the genital organs, the Y-shaped forks present on the proximal part of inner wall of the penis were observed exclusively in most anatomically studied Laeocathaica species among the Chinese dart-sac-bearing camaenids.   , HBUMM00069-spec.1 D L. carinalis Chen & Zhang, 2004     A general view, HBUMM08439spec.1 B left view of dart sac apparatus, HBUMM08439-spec.1 C ventral view of dart sac apparatus, HBUMM00069-spec.1. Abbreviations: AS -accessory sac; At -atrium; BC -bursa copulatrix; BCDbursa copulatrix duct; DS -dart sac; DtC -a chamber containing love dart; Ep -epiphallus; FO -free oviduct; MG -mucous glands; P -penis; PAS -proximal accessory sac; PR -penial retractor muscle; PS -penial sheath; Va -vagina; VD -vas deferens. Asterisk * indicates the opening of proximal accessory sac.
Additional information of shell. Very fine and slim granules (~ 20 μm long) are present on the protoconch. After the fourth whorl, including the umbilical region, irregularly arranged spiral grooves are present. On teleoconch whorls, the growth lines are low and indistinct.
General anatomy. Eversible head wart lowly present. Jaw arcuate, with five projecting ribs.
Remarks. By shell sculpture, including that on the protoconch, this species (Fig. 46G, H) cannot be immediately distinguished from Laeocathaica tropidorhaphe (Fig. 46I, J) and L. distinguenda (Fig. 46A, B). It seems that L. tropidorhaphe forms a continuous variation of shell shape and the conchological delimitation among these three species that are geographically coexistent is not so distinct (Páll-Gergely et al. 2022). According to our observation, the key morphological features to practically distinguish the three species are: (1) brownish/chestnut coloration. In Laeocathaica amdoana such coloration is usually (!) obviously darker and in L. distinguenda the coloration is usually very pale (in our Fig. 15C, it is a relatively darker shell). However, in HBUMM05479 (dissected, shell not pictured) the shell is in very pale dirty yellow except peripherally whitish.
(3) the structure of umbilicus. In both Laeocathaica amdoana and L. tropidorhaphe, the umbilicus is funnel-shaped and through which every whorl is visible. However, in Laeocathaica distinguenda, the penultimate whorl is much projecting and makes a suddenly enlarged umbilicus (Möllendorff 1899;our own observation, e.g., to compare Fig. 15 with Figs 5A, B, 33). Laeocathaica amdoana, L. distinguenda, and L. tropidorhaphe are clearly distinguishable based on genital features. Laeocathaica amdoana and L. tropidorhaphe, both of which have a long vagina between dart sac apparatus and atrium that was not seen in L. distinguenda, can be distinguished by the presence of proximal accessory sac in the former species. Laeocathaica tropidorhaphe belongs to the three species in Laeocathaica that have no proximal accessory sac. In Laeocathaica amdoana there are two tiny proximal accessory sacs, and each has an opening leading to the dart sac chamber, which means the proximal accessory sacs could be functional compared to the blind one (i.e., without opening) observed in Pseudiberus tectumsinense pingi (Zhang et al. 2021). In addition, in Laeocathaica amdoana the dart is apically 2-bladed rather than 4-bladed in L. tropidorhaphe.
The phylogeny based on ITS2 and 16S suggests that Laeocathaica amdoana is sister to L. distinguenda and L. tropidorhaphe (Fig. 51). In Chen and Zhang (2004: 316, fig. 303), the species identified as Laeocathaica amdoana is dubious and looks like a L. distinguenda. For more comments, see Laeocathaica tropidorhaphe.

Laeocathaica anceyi (Möllendorff in Ancey, 1889)
Helix anceyi Möllendorff  Additional information of shell. In juveniles, regularly arranged fine threads and elongate granules are present on the protoconch, where in adults such sculpture is difficult to be observed because of erosion. Spiral grooves are present after the fourth whorl or only on apical body whorl, but are absent in umbilical side. The teleoconch has distinct and regularly arranged ribs, among which there is no fine threads.
General anatomy. Eversible head wart not prominent, perhaps due to specimen of not full maturity. Jaw arcuate, with five projecting ribs.
Anatomy of genital organs. Penial sheath moderately long, covering ~ 1/4 of penis. Penis slightly expanded distally. Accompanied with two or three lower pilasters, at proximal 1/2 of penis two thin penial pilasters fusing into one Y-shaped fork. Fine pilasters of distal 1/2 penis weaving into delicate net. Near epiphallic opening numerous fine pilasters merging into ~ 4 short but thick folds. Vas deferens narrow throughout. Vagina between atrium and dart sac not elongated. Vagina between dart sac and insertion of bursa copulatrix duct ~ 1/2 length of dart sac. Dart sac ~ 2/3 length of penis. Information of love dart unknown. Accessory sac small. Mucous glands ~ 4, each complicatedly branched. Proximal accessory sacs two, symmetrical on dart sac, dorsally separated and ventrally touching, internally smooth (without pilasters), each with an opening leading to dart chamber near dart chamber opening. Bursa copulatrix duct of even diameter.    Additional information of shell. On adult shell the protoconch is granulate with thick granules of ~ 40 μm long, each of which looks like a hump in a pit. The obscurity of such granules is caused by erosion or weathering. Spiral grooves are absent throughout the shell. On teleoconch the growth lines are low but distinct.
General anatomy. Eversible head wart weak. Jaw arcuate, with four or five projecting ribs.
Anatomy of genital organs. Penial sheath moderately long, covering ~ 1/4-1/3 of penis. Penis somewhat expanded distally. A pair of penial internal pilasters fusing into one Y-shaped fork at proximal 1/3, and another pair fusing into one Y-shaped fork at proximal 1/2 of penis; some other low pilasters variably present. Distally inside penis, numerous fine pilasters merging into 6-8 short but thick folds near opening of epiphallus. Vas deferens narrow throughout. Vagina between atrium and dart sac not elongated. Vagina between dart sac and insertion of bursa copulatrix duct approximately as long as or slightly shorter than 2/3 of dart sac. Dart sac ~ 1/2 of penis. Love dart ~ 2 mm long. Accessory sac spherical, internally almost solid, inserting into dart sac medially, opening to distal dart chamber. Mucous glands six or seven, each simply or complicatedly branched. Proximal accessory sacs two, asymmetrical, left one larger than right one, dorsally separated and ventrally touching, with internal pilasters, each with an opening leading to proximal dart chamber. Bursa copulatrix duct of even diameter. Bursa copulatrix ovate, small.

Museum
Additional information of shell. Tiny granules (~ 5 -~ 50 μm) are densely and radially arranged throughout the protoconch. The erosion or weathering of sculpture on adult shell is not observed. Spiral grooves are absent throughout the shell. On teleoconch the growth lines are usually indistinct.
General anatomy. Eversible head wart weakly present. Jaw arcuate, with four projecting ribs.
Anatomy of genital organs. Penial sheath covering ~ 1/3 of penis. Penis tubular and equally thick. Inside penis, 5-6 narrow or thick pilasters present, Y-shaped fork formed by adjacent pilasters absent. Fine pilasters on distal end of penis merging into seven or eight thick folds. Vas deferens narrow throughout. Vagina between atrium and dart sac not elongated. Vagina between dart sac and insertion of bursa copulatrix duct ~ 1/2 length of dart sac. Dart sac slightly shorter than penis. Love dart ~ 5 mm long, apically 2-bladed. Accessory sac small but externally distinct, internally empty but spatially narrow, inserting into dart sac at middle part, opening to distal dart chamber. Mucous glands four (HBUMM04204-spec.14, spec.16) or five (HBUMM04204spec.13, HBUMM01251a-spec.1), each complicatedly branched. Proximal accessory sacs two, symmetrical or the left one slightly larger (HBUMM04204-spec.14), dorsally and ventrally separated, each with a distal opening leading to dart chamber near its opening. Bursa copulatrix duct of even diameter. Bursa copulatrix ovate, small.
Remarks. This species is not known from NW Sichuan, so the specimens distributed in "Wentschun" [Wenchuan 汶川] identified as Cathaica christinae by Blume (1925;followed by Yen 1938), may indicate some other sinistral species. However, it could also be an erroneous site naming, as all field records except this indicate that no Laeocathaica species is distributed in Wenchuan.   Anatomy of genital organs. Penis as long as dart sac, distally expanded. Vas deferens narrow throughout. Vagina between atrium and dart sac not elongated. Vagina between dart sac and insertion of bursa copulatrix duct ~ 1/2 length of dart sac. Love dart ~ 2 mm long, apically 2-bladed. Accessory sac small but distinguishable from outside, inserting into dart sac at middle part, opening to distal dart chamber. Mucous glands two, each complicatedly branched. Bursa copulatrix duct of equal thickness, as long as dart sac. Bursa copulatrix ovate (Wu 1999: 148, fig. 6.13-1).  Distribution. Gansu: Wenxian (type locality), Wudu (type locality), Zhouquxian (type locality); Sichuan: Jiuzhaigouxian (type locality).

Laeocathaica distinguenda
Additional information of shell. The protoconch has the widespread granules each of which is ~ 20 -~ 40 μm long and looks like a hump embedded in a shallow socket. All granules are present on densely arranged fine radial threads. Spiral grooves are shallowly present. The growth lines on teleoconch are more or less distinct but are irregularly arranged.
General anatomy. Eversible head wart present. Jaw arcuate, with 4-7 projecting ribs. Anatomy of genital organs. Penial sheath moderately long, covering ~ 1/6-1/4 of penis. Penis slightly expanded distally. Inside penis, two penial pilasters forming one Yshaped fork at proximal 1/3 penis (only indistinct in HBUMM05417); a rather thick pilaster that is made up of numerous thread-like longitudinal folds occupying proximal 1/3-2/3 of penis. Pilasters of median to distal penis weaving into a delicate net that bears regularly arranged diamond-shaped papillae, which are usually lost perhaps because of bad specimen condition. Distally inside penis, fine pilasters merging into 6-9 short and more or less thick folds near opening of epiphallus. Vas deferens narrow throughout. Vagina between atrium and dart sac not elongated. Vagina between dart sac and insertion of bursa copulatrix duct ~ 1/4 length of dart sac. Dart sac ~ 1/2 length of penis. Love dart ~ 9 mm long, apically 2-bladed. Accessory sac small but distinguishable from outside, internally solid, inserting into dart sac at middle part, opening to distal dart chamber. Mucous glands 4 (HBUMM08429, each complicatedly branched) -12 (HBUMM05479, simply branched). Proximal accessory sacs two, symmetrical or the right one slightly larger, separated dorsally and ventrally, with a few internal pilasters, each with an opening leading to dart chamber near opening of dart chamber. Bursa copulatrix duct of even diameter. Bursa copulatrix ovate.
Remarks. The sculpture on protoconch and teleoconch of this species (Fig. 46A, B) resembles that of Laeocathaica amdoana (Fig. 46G, H). However, in Laeocathaica distinguenda, as in the most congeners of Laeocathaica, the part of the vagina between atrium and dart sac apparatus is not elongated.

Laeocathaica dityla
Additional information of shell. Tiny, low and sparsely arranged granules (~ 10 μm) on the smooth protoconch are present but difficult to be observed because of erosion or weathering. Spiral grooves are absent throughout the shell. On teleoconch the growth lines are not observed except on the part just following the protoconch.
General anatomy. Eversible head wart present but not prominent. Jaw arcuate, with four or five projecting ribs.
Anatomy of genital organs. Penial sheath rather short, covering ~ 1/8 of penis. Penis tubular and equally thick. Inside penis, two penial internal pilasters forming one Y-shaped fork at proximal 1/2 of penis, accompanied with another two thicker pilasters. Distal 1/2 of penis occupied by numerous isolated minute diamond-shaped papillae. Vas deferens narrow throughout. Vagina between atrium and dart sac not elongated. Vagina between dart sac and insertion of bursa copulatrix duct approximately as long as dart sac. Dart sac ~ 1/2 length of penis. Love dart ~ 4 mm long, apically 2-bladed and then rounded. Accessory sac small but distinguishable from outside, internally empty but spatially narrow, inserting into dart sac medially, opening to distal dart chamber. Mucous glands two (HBUMM00698-spec.2, spec.3) or three (HBUMM00698-spec.1), each a single tube. Proximal accessory sacs two, dorsally and ventrally touching, without internal pilasters, each with an opening leading to dart chamber near its opening. The right proximal accessory sac somewhat larger and with thicker wall than the left one. Bursa copulatrix duct basally slightly expanded. Bursa copulatrix ovate.
Remarks. This species has a very unique shell, but the anatomy of the terminal genitalia coincides with those of the congeners.  Table 1 Cathaica (Laeocathaica) dolani Pilsbry, 1934: 16, pl. 3, fig. 4, 4a-c.    Additional information of shell. The shell is covered with radially arranged low scales of variable length (~ 25 -~ 300 μm long) everywhere. The size (esp. length) of scales increase from protoconch to body whorl. Spiral grooves are absent throughout the shell.
Anatomy of genital organs. Penial sheath covering ~ 1/4-1/3 of penis. Penis short, thick, distally expanded. Inside penis, two thick and prominent pilasters fusing into one Y-shaped fork at proximal 1/3-1/2 penis, accompanied with ~ 6 narrower or equally thick pilasters nearby. Pilasters on distal end of penis not merging into thick folds. Vas deferens narrow throughout. Vagina between atrium and dart sac not elongated. Vagina between dart sac and insertion of bursa copulatrix duct ~ 1/2 length of dart sac. Dart sac approximately as long as penis. Love dart ~ 5 mm long, apically with cross-section rhombic. Accessory sac small, internally empty, inserting into dart sac at middle part, opening to distal dart chamber. Mucous glands two (HBUMM00069spec.1-3), each complicatedly branched. Proximal accessory sac one, large, on right side of dart sac, with an opening leading to dart chamber near its opening. Bursa copulatrix duct basally slightly expanded. Bursa copulatrix elongate, ovate.
Remarks. In Laeocathaica, Laeocathaica dolani is the only species with only one proximal accessory sac. In addition, this species is unique in the genus that it keeps periostracum scales throughout its lifetime.  Distribution. Hubei: Badong (type locality), Yichang (Changyang); Sichuan (Emei); Chongqing: Fengjie.
Additional information of shell. Sculpture on the protoconch was present but indistinct because of erosion or weathering. Spiral grooves are absent throughout the shell.
General anatomy. Eversible head wart low. Jaw arcuate, with four or five projecting ribs.
Anatomy of genital organs. Penial sheath moderately long, covering ~ 1/4-1/3 of penis. Penis slightly expanded distally. A pair of penial internal pilasters fusing into one Y-shaped fork at proximal 1/3; ~ 2 larger pilasters present nearby. Distally inside penis, numerous fine pilasters merging into 6 to 8 short but thick folds near opening of epiphallus. Vas deferens narrow throughout. Vagina between atrium and dart sac not elongated. Vagina between dart sac and insertion of bursa copulatrix duct approximately equal to or slightly shorter than 2/3 length of dart sac. Dart sac ~ 1/2 length of penis. Love dart ~ 2 mm long. Accessory sac spherical, internally almost solid, inserting into dart sac medially, opening to distal dart chamber. Mucous glands 5-7, each complicatedly branched. Proximal accessory sacs two, symmetrical, dorsally separated and ventrally touching, with a few internal pilasters, each with an opening leading to proximal dart chamber. Bursa copulatrix duct of even diameter. Bursa copulatrix ovate, small.
Remarks. This species has a spire of variable height, from flatness to dome shape. The umbilicus of this species is obviously narrower than that of Laeocathaica christinae. Furthermore, this species has a pair of ventrally touching proximal accessory sacs instead of ventrally separated ones, which are observed in L. christinae.

Laeocathaica odophora
General anatomy. Eversible head wart present but not prominent. Jaw arcuate, with seven projecting ribs.
Anatomy of genital organs. Penial sheath short, covering ~ 1/6 of penis. Penis tubular and equally thick. Inside penis, ~ 5 low pilasters present proximally, two high pilasters fusing into one Y-shaped fork at proximal 1/4. Fine pilasters on distal end of penis not merging into thick folds. Vas deferens narrow throughout. Vagina between atrium and dart sac not elongated. Vagina between dart sac and insertion of bursa copulatrix duct ~ 1/2 length of dart sac. Dart sac ~ 1/2 length of penis. Love dart ~ 4.5 mm long, apically 2-bladed. Accessory sac small but externally distinguishable, internally solid, inserting into dart sac at distal 1/3, opening to dart chamber. Mucous glands 5 (HBUMM08430-spec.1), each singly tubular or simply branched. Proximal accessory sacs two, asymmetrical with the right one distinctly larger, apically separated and ventrally touching, each centrally with an opening (rounded, diameter ~ 0.2 mm) leading to proximal dart chamber. Bursa copulatrix duct of even diameter. Bursa copulatrix ovate, small.
Remarks. This species has a pair of asymmetrical and ventrally touching proximal accessory sacs that is rarely observed in the genus. In comparison, its conchologically similar species Laeocathaica zhengpingliui Wu, sp. nov. has a pair of symmetrical proximal accessory sacs that are ventrally separated from each other.

Laeocathaica pewzowi
General anatomy. Head with flat but distinct eversible head wart. Jaw arcuate, with four projecting ribs.
Anatomy of genital organs. Penial sheath covering ~ 1/9 of penis. Penis tubular and distally thicker. Inside penis, ~ 4 high parallel pilasters on proximal 2/3, at proximal ~ 1/4 two weak pilasters fusing into one Y-shaped fork. Fine pilasters on distal end of penis merging into ~ 7 thin or thick folds. Vas deferens narrow throughout. Vagina between atrium and dart sac not elongated. Vagina between dart sac and insertion of bursa copulatrix duct ~ 1/2 length of dart sac. Dart sac ~ 2/5 length of penis. Accessory sac tiny, internally solid, inserting into dart sac at middle part, opening to dart chamber. Mucous glands four, each singly tubular or simply branched. Proximal accessory sacs two, of similar size and symmetrical, apically separated and ventrally touching, each distally with an opening leading to proximal dart chamber. Bursa copulatrix duct of even diameter. Bursa copulatrix long-ovate.
Remarks. The species has the most common pattern of the dart sac apparatus of the genus, i.e., two equally-sized and ventrally touching proximal accessory sacs, each with an opening leading to the dart chamber; this has been observed in ten of the 21 species anatomically studied herein. This species can be immediately recognized by its particular shell morphology.

Distribution. Gansu: Wenxian (type locality).
Additional information of shell. The first 1 1 / 4 protoconch whorls are almost smooth, and the subsequent 1/4 whorls have dense radially arranged fine threads. Spiral grooves are regularly present throughout body whorl.
Anatomy of genital organs. Penial sheath covering ~ 1/5 of penis. Penis tubular and distally thicker. Inside penis, ~ 7 high parallel pilasters on proximal 1/2, no pilasters fusing into Y-shaped fork. Fine pilasters on distal end of penis merging into 9-12 thin or thick folds. Vas deferens narrow throughout. Vagina between atrium and dart sac extremely elongated, ~ 4× longer than dart sac. Vagina between dart sac and insertion of bursa copulatrix duct approximately as long as dart sac. Dart sac ~ 1/6 length of penis. Love dart ~ 1.5 mm long, apically 2-bladed. Accessory sac tiny, internally empty, inserting into dart sac at middle part, opening to dart chamber. Mucous glands eight, each singly tubular or simply branched. Proximal accessory sac absent. Bursa copulatrix duct equally thick.
Remarks. This species is one of the three species that do not have proximal accessory sac on dart sac apparatus. However, the shell morphology of Laeocathaica phaeomphala differs greatly from that of the other two species L. polytyla and L. tropidorhaphe.  General anatomy. Eversible head wart prominent. Jaw arcuate, with three projecting ribs.

Laeocathaica polytyla
Anatomy of genital organs. Penial sheath covering ~ 1/4 of penis. Penis proximately tubular and distally expanded. Inside penis, two pilasters fusing into one Y-shaped fork at proximal 1/5, two more pilasters of similar thickness also present. Fine pilasters on distal end of penis merging into ~ 8 thick folds. Vas deferens narrow throughout. Vagina between atrium and dart sac not elongated. Vagina between dart sac and insertion of bursa copulatrix duct ~ 1/2 length of dart sac. Dart sac ~ 1/2 length of penis. Love dart ~ 1 mm long, apically 2-bladed. Accessory sac small but externally distinguishable, internally solid, inserting into dart sac at distal 1/3, opening to dart sac chamber. Mucous glands four or five, each singly tubular or simply branched. Proximal accessory sac absent. Bursa copulatrix duct equally thick.
Distribution. Gansu: Wenxian (type locality). Additional information of shell. Granules on protoconch can only be unclearly and partially observed near suture because of erosion or weathering in adults. Granules are short (~ 20 μm long) on fine threads. Spiral grooves are absent throughout. On teleoconch whorls, fine threads are present between every two adjacent ribs.
General anatomy. Eversible head wart present. Jaw arcuate, with five projecting ribs.

Laeocathaica prionotropis
Remarks. The most distinctive character of the genitalia of Laeocathaica prionotropis is the lump formed by the fusing pilasters in the penis.
Anatomy of genital organs. Penial sheath very short, covering ~ 1/10 of penis. Penis tubular, equally thick. Inside penis, two high pilasters forming one Y-shaped fork at proximal 1/5, besides with two pilasters parallelly merging into one thickest pilaster. Fine pilasters on distal end of penis merging into ~ 6 thick folds, among which one is thicker than the others. Vas deferens narrow throughout. Vagina between atrium and dart sac not elongated. Vagina between dart sac and insertion of bursa copulatrix duct ~ 1/2 length of dart sac. Dart sac ~ 1/2 length of penis. Love dart ~ 9 mm long, apically 2-bladed, subsequently rounded. Accessory sac small, internally solid, inserting into dart sac at middle part, opening to dart chamber. Mucous glands ~ 5, each complicatedly branched. Proximal accessory sacs two, symmetrical, separated apically and touching ventrally, each with an opening leading to proximal dart chamber near dart chamber opening. Bursa copulatrix duct of even diameter. Bursa copulatrix ovate, very small.
Remarks. Geographically, the distribution of Laeocathaica carinifera in the Yangtze valley in Chongqing and Sichuan does not overlap those of L. stenochone and L. qingchuanensis Wu, sp. nov., both of which occur along the Bailongjiang River (Fig. 2C). In terms of shell morphology, Laeocathaica stenochone close to L. carinifera and L. qingchuanensis Wu, sp. nov. can be distinguished (Fig. 50B). Laeocathaica stenochone shows a particular protoconch and teleoconch sculpture (Fig. 46C, D), which is completely different from those of L. carinifera (Fig. 45I, J). In molecular analysis based on present combination of 16S + ITS2 sequences (Fig. 51), Laeocathaica stenochone (voucher HBUMM08431a) cannot be distinguished from L. carinifera (voucher HBUMM05103, HBUMM05131) because they share the same ITS2 sequence and show only 3-site difference in 16S sequence, suggesting they are possibly genetically very close species. However, L. stenochone and L. carinifera cannot be treated as one species (see Discussion).
Remarks. In terms of shell shape, this species has an obviously depressed spire and more or less sharp carina or angulation above periphery compared to the sympatric (Fig. 2D) Laeocathaica amdoana and L. distinguenda. Their shell differences are also indicated by the average shapes showed in Fig. 50A. The aperture of Laeocathaica tropidorhaphe, more or less stretched outwards, is narrower than that of L. distinguenda (Fig. 50A). Laeocathaica dangchangensis Chen & Zhang, 2004 shows a typical shell of L. tropidorhaphe (Fig. 50A).
The systematic affinity between Laeocathaica amdoana, L. distinguenda and L. tropidorhaphe is supported by the phylogeny resulting from the present analyses (Fig. 51), which also indicates that the character state of the presence of proximal accessory sacs may have repeated on different branches of Clade M (Laeocathaica) (Fig. 51).
For more comments, see Laeocathaica amdoana. Measurement of holotype. Shell height 6.9 mm, maximum diameter 15.6 mm, aperture height 3.9 mm, aperture breadth 5.8 mm, umbilicus diameter 5.0 mm, protoconch whorls 1 1 / 2 , whorls 8 7 / 8 . Diagnosis. Protoconch with dense radially-arranged threads, visible through umbilicus. Beneath carina a clear chestnut band present. Mucous glands four or five. Penis with two pairs of pilasters fusing into two Y-shaped forks. Vagina between atrium and dart sac not elongated. Proximal accessory sac absent.

New taxa of
Description of shell. Sinistral, depressed, thin but somewhat solid. Shell with 8 1 / 8 -9 3 / 8 fairly flat whorls. Suture impressed. Protoconch 1 1 / 2 -1 3 / 4 whorls, with densely arranged radial threads that may be invisible because of weathering or erosion. Periphery distinctly angulate. Growth lines indistinct. Spiral grooves are absent throughout. Aperture oblique, roundly square, descending in front. Peristome not expanded and indistinctly reflexed at lower part. Within aperture a ring-like thickening present, basally with a flat tooth. Columella oblique. Umbilicus abruptly broadened after penultimate whorl, ~ 1/4 of maximum diameter. Protoconch visible through umbilicus. Shell apically in intermittent yellowish white and pale chestnut patches except white carina. In umbilical view shell distinctly paler in greyish yellow, just beneath carina a clear chestnut band present, umbilical region brownish.
Anatomy of genital organs. Penial sheath covering ~ 1/5 of penis. Penis distally fairly expanded. Inside penis, two high pilasters fusing into one Y-shaped fork at proximal 1/4, another pair of pilasters fusing into one Y-shaped fork at middle part. Fine pilasters on distal end of penis merging into ~ 7 thick and short folds. Epiphallic papilla absent. Vas deferens narrow throughout. Vagina between atrium and dart sac not elongated. Vagina between dart sac and insertion of bursa copulatrix duct ~ 1/2 length of dart sac. Dart sac ~ 1/2 length of penis. Accessory sac small but externally distinguishable, internally solid, ventrally inserting into dart sac at distal 1/3, together with mucous glands opening to dart chamber. Mucous glands four or five, each singly tubular or bifurcated. Proximal accessory sac absent. Bursa copulatrix duct equally thick.
Etymology. The name of this new species is made up of para-meaning similar to and polytyla from Laeocathaica polytyla Möllendorff, 1899, which is conchologically close to the new species.
Ecology. On rocks of local hill. Distribution. Only known from the type locality.

Remarks.
The new species exhibits a large intraspecific change in size (Fig. 25), which is also showed in Laeocathaica polytyla (Fig. 24A, B). Laeocathaica parapolytyla Wu, sp. nov. looks like a flattened and sharply carinate L. polytyla, but has slightly different coloring and coarser growth lines. The terminal genitalia of these two species are similar, but in the new species the penis internally has two pairs of pilasters that fuse into two Y-shaped forks, while in Laeocathaica polytya the penis has only one Y-shaped fork formed by adjacent pilasters. Measurement of holotype. Shell height 8.1 mm, maximum diameter 23.7 mm, aperture height 5.6 mm, aperture breadth 10.6 mm, umbilicus diameter 5.6 mm, protoconch whorls 1 1 / 2 , whorls 5 5 / 8 . Diagnosis. Protoconch with decussate radial and spiral threads. Umbilicus broad and deep, through which protoconch is visible. A bright band present between carina and suture. Beneath carina a dark chestnut band present. Mucous glands two. Penis with two proximal thick internal pilasters fusing into a Y-shaped fork at proximal 1/3. Vagina between atrium and dart sac not elongated. Two proximal accessory sacs on both sides of dart sac, with two pores leading to opening of dart chamber. Description of shell. Sinistral, depressed, thin but somewhat solid. Shell with 5 1 / 2 -5 7 / 8 fairly flat whorls. Suture impressed. Protoconch 1 1 / 2 -1 5 / 8 whorls, with decussate radial and spiral threads, on the first whorl of which may be invisible Table 2. Shell measurements (range, mean ± s.d.) of the new species of Laeocathaica Möllendorff, 1899 described in this work (length in mm). Wu, sp. nov., HBUMM08298-spec.1, holotype A general view B ventral view of dart sac apparatus C left view of dart sac apparatus D cross-section of dart sac at the position arrowed in (A). Abbreviations: AS -accessory sac; At -atrium; BC -bursa copulatrix; BCD -bursa copulatrix duct; DS -dart sac; DtC -a chamber containing love dart; Ep -epiphallus; FO -free oviduct; MG -mucous glands; P -penis; PAS -proximal accessory sac; PO -opening of proximal accessory sac leading to dart chamber; PR -penial retractor muscle; PS -penial sheath; Va -vagina; VD -vas deferens. because of weathering or erosion. Growth lines fine, more or less clear. Aperture oblique, peach-shaped, descending. Peristome expanded and reflexed at lower part. Columella oblique. Umbilicus broad, ~ 1 / 3 of maximum diameter. Protoconch visible through umbilicus. Shell apically in chestnut except white carina, after the first three or four whorls a bright band present between carina and adjacent suture. In umbilical view shell distinctly paler in greyish yellow and just beneath carina a chestnut band present.

Figure 36. Genital anatomy of Laeocathaica qishilii
General anatomy. Eversible head wart present. At mantle edge leaf-shaped appendage absent. On internal body wall of head region between ommatophorous insertions with neither glands nor tiny pits. Body greyish brown, central dorsum with pale longitudinal stripes. Sole dirty white. Jaw arcuate, with 3-5 more or less projecting ribs.
Anatomy of genital organs. Penial sheath short but well developed. Penis of equal thickness, externally simple. Inside penis, two very thick longitudinal pilasters fusing into a Y-shaped fork at proximal 1/3, accompanied with another two thick pilasters, these plasters then change into numerous fine pilasters that distally merge into three short but thick folds near opening of epiphallus. Epiphallic papilla absent. Vas deferens narrow throughout. Vagina between atrium and dart sac not elongated. Accessory sac spherical, solid, inserting into dart sac medially, opening to distal dart chamber. Mucous glands two, each complicatedly branched. Proximal accessory sacs two, symmetrical, dorsally separated and ventrally touching, each with a pore leading to proximal dart chamber. Love dart ~ 6 mm long, apically 2-bladed, medially round-hexagonal. Bursa copulatrix duct equally narrow. Bursa copulatrix pear-shaped.
Etymology. This new species is named after Mr Li, Qi-Shi, who made this work possible with his field work.
Ecology. This species is found under rotten wood. Distribution. Only known from the type locality.
Remarks. This new species has a unique protoconch on which decussate radial and spiral threads are present compared to the granulation on this part in the other Laeocathaica species. The new species is conchologically close to Laeocathaica prionotropis, but the former species is apically more depressed, more broadly umbilicate, has a more expanded peristome, a more elongated aperture due to the more prominent carina, is apically evenly brown, and has a smooth shell surface instead of the finely scaly surface in the latter species. The new species shares the inner structure of the dart sac with L. prionotropis. However, they differ in the internal structure of penis: in L. prionotropis, partial pilasters merge into a tubercle, which is missing in the new species. They also differ in the number of tubes of the mucous glands. Type material. Holotype HBUMM08422-spec.1, fms, a slope near X496 (32.969442°N, 104.654191°E), Wenxian, Gansu Province; 2019-X-13; coll. Li, Q.-M.; DNA voucher HBUMM08422a. Paratypes HBUMM08422-spec.2, 1 animal with mature shell but immature genitalia, dissected; same data as holotype. HBUMM08448, 7 fms, east of town of Wenxian, 2020-VIII, coll. Chen, Z.-G.
General anatomy. Eversible head wart small but prominent. At mantle edge leafshaped appendage absent. On internal body wall of head region between ommatophorous insertions with neither glands nor tiny pits. Body greyish brown, central dorsum with pale longitudinal stripes. Sole dirty white. Jaw arcuate, with five projecting ribs.
Anatomy of genital organs. Penial sheath present. Vagina between atrium and dart sac not elongate. Mucous glands four (observations of the genitalia of this species are only based on the paratype HBUMM08422-spec.2).
Etymology. This new species is named after the collector Mr. Qiming Li.
Ecology. In October, this species was found in the crevices of broken stones on dry slope.
Distribution. Only known from the type locality.
Remarks. This species has the strongest ribs on the shell surface and the broadest umbilicus of all species of Laeocathaica. Measurement of holotype. Shell height 10.0 mm, maximum diameter 19.6 mm, aperture height 5.6 mm, aperture breadth 7.5 mm, umbilicus diameter 7.0 mm, protoconch whorls 1 5 / 8 , whorls 9 1 / 4 . Diagnosis. Protoconch without granules. Umbilicus more than 1 / 3 maximum diameter, through which protoconch is visible. Beneath carina a chestnut band present. Palatal with two blunt teeth. Mucous glands six. Proximal 4/5 of penis with ~ 6 thick internal pilasters. Two adjacent pairs of penial pilasters fusing into two Y-shaped forks at distal 2/3 of penis. Vagina between atrium and dart sac moderately elongated. Proximal accessory sacs two, separate, symmetrical, each with a pore leading to opening of accessory sac.

Laeocathaica zhengpingliui
Description of shell. Sinistral, depressed, thin but somewhat solid. Shell with 8 5 / 8 -9 1 / 4 fairly flat whorls. Suture impressed. Protoconch 1 1 / 2 -1 3 / 4 whorls, with very fine axial striae which may be invisible on the first whorl possibly by weathering or erosion. Growth lines thick or rib-like above but fine beneath carina. Above periphery a sharp whitish carina present. Aperture oblique, peach-shaped, slightly descending in front. On ring-like thickening within aperture, a blunt tooth present near columella and another one near carina. Peristome almost not expanded, just minutely reflexed at lower part. Columella oblique. Umbilicus with a tint of pale brown, broadly conical, more than 1/3 of maximum diameter. Protoconch visible through umbilicus. Whorls apically in yellowish white with intermittent brownish patches. In umbilical view shell yellowish white with several brownish patches, and just beneath carina a chestnut band present.
General anatomy. Eversible head wart lowly present. At mantle edge leaf-shaped appendage absent. On internal body wall of head region between ommatophorous insertions with neither glands nor tiny pits. Body greyish brown, central dorsum with pale longitudinal stripes. Sole dirty white. Jaw arcuate, with ~ 6 more or less projecting ribs.
Anatomy of genital organs. Penial sheath very short. Penis distally slightly expanded, externally simple. Penis of proximal 4/5 internally with ~ 6 thick longitudinal pilasters, two adjacent pairs of which fuse into two Y-shaped forks at distal 2/3; pilasters then branching into fine pilasters that are connected to form network. Epiphallic papilla absent. Vas deferens narrow throughout. Vagina between atrium and dart sac somewhat elongated. Accessory sac spherical, empty, inserting into dart sac at middle part, opening near the opening of dart chamber. Mucous glands six, each a single tube or simply branched. Proximal accessory sacs two, separate, symmetrical, each with a pore leading to opening of accessory sac/dart chamber. Love dart ~ 5 mm long, rounded and bladeless throughout. Bursa copulatrix duct equally narrow.
Ecology. This species is found on exposed slate rocks of hill side. Distribution. This species is only known from the type locality.

Remarks.
The new species is conchologically close to Laeocathaica odophora; however, its carina is blunter, the aperture has only two weak teeth near the columella instead of two strong apertural teeth in the latter species, and the umbilicus is significantly broader. Regarding genitalia, the new species has two separated proximal accessory sacs of equal size, while in Laeocathaica odophora two proximal accessory sacs are ventrally adjacent and separated only by a very thin membrane, and the much smaller right proximal accessory sac makes L. odophora have an asymmetrical dart sac. Measurement of holotype. Shell height 9.0 mm, maximum diameter 19.3 mm, aperture height 5.6 mm, aperture breadth 7.3 mm, umbilicus diameter 7.1 mm, protoconch whorls 1 5 / 8 , whorls 9 1 / 8 . Diagnosis. Protoconch with elongated granules. Umbilicus suddenly narrowed from penultimate whorl, more than 1 / 3 maximum diameter, through which proto-conch is visible. Beneath carina a chestnut band present. Mucous glands four. Proximal 1/2 of penis with ~ 5 thin internal pilasters, two of them fusing into a Y-shaped fork at middle part. Distal region of penis with tongue-shaped papillae. Vagina between atrium and dart sac not elongated. Proximal accessory sacs two, symmetrical, each with a pore leading to dart chamber.

Laeocathaica cheni
Description of shell. Sinistral, depressed, somewhat solid. Shell with 9-9 5 / 8 fairly flat whorls. Suture impressed. Protoconch 1 1 / 2 -1 5 / 8 whorls, with fine granules (each ~ 20 μm long) almost invisible because of weathering or erosion. Growth lines thick or rib-like above but fine below carina. Above periphery a whitish carina present. Aperture oblique, peach-shaped, descending. On ring-like thickening within aperture, a very blunt tooth present near columella. Peristome almost not expanded, just minutely reflexed at lower part. Columella oblique. Umbilicus brownish, more than 1/3 of maximum diameter, suddenly narrowed from penultimate whorl. Protoconch visible through umbilicus. Whorls apically yellowish brown with intermittent darker brown patches. In umbilical view shell yellowish white with several brownish patches, and just beneath carina a thick chestnut band present.
General anatomy. Eversible head wart weakly present. At mantle edge leafshaped appendage absent. On internal body wall of head region between ommatophorous insertions with neither glands nor tiny pits. Body greyish brown, central dorsum with pale longitudinal stripes. Sole dirty white. Jaw arcuate, with ~ 8 more or less projecting ribs.
Anatomy of genital organs. Penial sheath short but well developed. Penis distally expanded, externally simple. Inside penis, proximal 1/2 with ~ 5 internal pilasters, two of which fuse into one Y-shaped fork at middle of penis; distal 1/2 with tongue-shaped (HBUMM05553b) or diamond-shaped papillae (HBUMM08428) that are erect or inclined towards atrium. Fine pilasters on distal end of penis merging into ~ 6 more or less thick short folds. Epiphallic papilla absent. Vas deferens narrow throughout. Vagina between atrium and dart sac not elongated. Accessory sac tiny, internally solid, inserting into dart sac medially, opening to dart chamber. Mucous glands four, each a single tube or simply branched. Proximal accessory sacs two, symmetrical, dorsally separated and ventrally touching each other, each with a ventral pore leading to proximal dart chamber. Love dart ~ 7 mm long, apically 2-bladed or rhombic (HBUMM08428spec.1) then rounded. Bursa copulatrix duct equally narrow.
Etymology. This new species is named in honor of Prof Chen, De-Niu, who works on land mollusks in the Institute of Zoology, Chinese Academy of Sciences, Beijing.
Ecology. This species is found on exposed slate rocks of the hill side. Distribution. Only known from the type locality.
Remarks. The new species is conchologically close to L. zhengpingliui Wu, sp. nov., but the new species has a much more depressed spire and relatively much larger aperture. In the genitalia, the middle part of penis, i.e., the distal 1/2 of the penis of the new species is occupied with regular tongue/diamond-shaped papillae (Fig. 44F, H), while in L. zhengpingliui Wu, sp. nov., the middle part is clearly short (only ~ 1/6 of the penis length) and does not have such tongue/diamond-shaped papillae (Fig. 44D). Measurement of holotype. Shell height 10.8 mm, maximum diameter 21.7 mm, aperture height 6.1 mm, aperture breadth 9.2 mm, umbilicus diameter 5.1 mm, protoconch whorls 1 1 / 2 , whorls 6 1 / 4 . Diagnosis. Protoconch with fine granules. Umbilicus moderately broad, through which protoconch is visible. Bluntly carinate slightly above periphery. Beneath carina a brown band present. Mucous glands 6-8. Approximately 1/2 of penis with three proximal thick internal pilasters, Y-shaped fork formed by adjacent pilasters absent. Vagina between atrium and dart sac moderately elongated. Proximal accessory sacs two, dorsally separated and ventrally touching, each with a pore leading to dart sac chamber near entrance of dart chamber.
General anatomy. Eversible head wart lowly present. At mantle edge leaf-shaped appendage absent. On internal body wall of head region between ommatophorous insertions with neither glands nor tiny pits. Body greyish brown, central dorsum with pale longitudinal stripes. Sole dirty white. Jaw arcuate, with 4-6 projecting ribs. Anatomy of genital organs. Penial sheath short. Penis distally swollen, externally simple. Proximal 1/2 penis with four thick internal pilasters which do not fusing, pilasters then branching into numerous fine pilasters that merge into ~ 6 short but thick (thickest in the genus) folds near opening of epiphallus. Vas deferens narrow throughout. Vagina between atrium and dart sac moderately elongated. Accessory sac spherical, internally with high pilasters and fairly solid inside, inserting into dart sac medially, opening to distal dart chamber. Mucous glands 6-8, each single tube or simply branched. PAS two, dorsally separated and ventrally touching, each with a pore leading to dart chamber near dart chamber opening. Proximal bursa copulatrix duct slightly expanded. Bursa copulatrix elongate ovate.
Etymology. This new species is named after name of the type locality Qingchuan, Sichuan Province.
Ecology. This species is found on slate rocks covered with mosses in a humid mountainous environment.
Distribution. Only known from the type locality.  Wu, sp. nov. is close to L. stenochone and L. carinifera in general shell shape, aperture shape and coloration, but the new species has a relatively higher shell (Fig. 50B) and the slimmest protoconch granules (Fig. 45E). The new species differs from Laeocathaica stenochone and L. carinifera in that it has both a long vaginal section above the dart sac and the inner structures of penis, where proximal parallel penial pilasters do not form the Y-shaped fork (Fig. 44E). In addition, compared to Laeocathaica carinifera (Fig. 10), the new species has a very short penial sheath and a pair of symmetrical proximal accessory sac (Fig. 40). Among the aforementioned three species, Laeocathaica stenochone has a relatively longer penis. Description of shell. Sinistral, depressed, thin but somewhat solid. Shell with 5-5 1 / 8 convex whorls. Suture impressed. Protoconch 1 1 / 2 -1 5 / 8 whorls, densely with tiny granules (each ~ 10 μm long) which are obscured by erosion or weathering. Growth lines indistinct. Shell in pale brown, strongly glossy, almost transparent. Body whorl shouldered above periphery, with a white band on shoulder. Aperture oblique, round, abruptly descending in front. A white thickening within aperture and thickened callus forming a continuous peristome. Peristome expanded and slightly reflexed at lower part. Columella oblique. Umbilicus very broad, ~ 1 / 2 of maximum diameter. Protoconch visible through umbilicus.  Etymology. This cute new species is named in memory of Hartmut Nordsieck, a German malacologist who showed strong interest in the snails of the South Gansu Plateau and was a good friend of the first author. Ecology. This species was found on bare earth with a few broken rocks. Distribution. Only known from two localities where the types were found. Remarks. The new species is the smallest species in Laeocathaica, where it is provisionally placed due to its chirality, granules on the protoconch and the similarity of the shell to  , HBUMM08439 C protoconch D teleoconch E, F L. nordsiecki Wu, sp. nov., HBUMM08446, paratype, subadult E protoconch F teleoconch G, H L. pewzowi Möllendorff, 1899, HBUMM08452 G protoconch H teleoconch I, J L. carinalis Chen & Zhang, 2004, HBUMM08453 I protoconch J teleoconch K, L L. zhengpingliui Wu, sp. nov., HBUMM05553-spec.2, paratype, juvenile K protoconch L teleoconch.

Phylogenetics
To investigate the systematic position of the putative Laeocathaica clade (because of the absence of type species of Laeocathaica L. christinae), 13 species of Laeocathaica and 33  Wu, sp. nov., Guoyuanxiang, Jiuzhaigou D L. qiminglii Wu, sp. nov., an indoor photograph E L. qingchuanensis Wu, sp. nov., Dagou Nature Reserve, Qingchuan County F L. cheni Wu, sp. nov., Hengdan, Wenxian. species of another 16 camaenid genera, whether or not they bear a dart sac, are included in the analyses ( Table 3). The final dataset contains sequences from 47 species including the outgroup Helix pomatia. Seventy-nine of the 94 original sequences have the unique combined sequence 16S + ITS2. The model "GTR+G+I" was selected as the best nucleotide substitution model for the combined dataset (lnL = -11126.1, BIC = 24124.9).
The phylograms produced by both Maximum Likelihood and Bayesian Inference based on partial 16S and partial ITS2 sequences are topologically identical in the major branches with the exception of different positions of two nodes (orange parts in Fig. 51). The phylogenetic trees are robust that their most nodes received strong support as showed by the high Bayesian posterior probability (BPP) and/or Maximum-likelihood bootstrap values (BP) (Fig. 51). The clades Nesiohelix, Satsuma and Traumatophora represent the most basal offshoot in the phylogenetic trees. In Fig. 51, those clades which include the type species of a genus are recognizable by lack of quotation marks around the generic name. So, the lineage separated under Figure 50. Scatter plots of canonical variate 1 against canonical variate 2 (Canonical Variate Analysis), showing the shell morphological relationships among A Laeocathaica distinguenda Möllendorff, 1899 (green dots; a, average shape), L. amdoana Möllendorff, 1899 (blue dots; b, average shape) and L. tropidorhaphe Möllendorff, 1899 (orange dots; c, average shape) B L. qingchuanensis Wu, sp. nov. (green dots; a, average shape), L. stenochone Möllendorff, 1899 (orange dots; b, average shape) and L. carinifera (H. Adams, 1870) (blue dots; c, average shape). Encircled dots: 1, SMF 8959, lectotype; 2, HBUMM05436-spec.1; 3, SMF 8952, lectotype; 4, SMF 9074, lectotype; 5, paratype of L. dangchangensis Chen & Zhang, 2004;6, SMF 9071, lectotype;7, syntype, NHMUK 1870.7.16.7. Data for 5 from fig. 7D, 6 and 7 from fig. 12 in Páll-Gergely et al. 2022. Clade D for example contains a clade that includes Helix similaris, the type species of Bradybaena. Subsequently, species which cluster here, in fact constitute members of that genus, while those clustering elsewhere and are commonly affiliated to  Table 1) based on the concatenated partial mitochondrial 16S and partial ITS2 sequences. The tree is rooted with Helix pomatia. Numbers near nodes indicating Bayesian posterior probabilities and Maximum-likelihood bootstrap values are given as BPP ⁄BP. Black or orange part shows the topology where the result yielded by using Bayesian-Inference method agrees with that by using Maximum-likelihood method or not, respectively. An asterisk indicates the branch is exactly one third shortened in length. Scale bar is for substitutions per site.
Bradybaena, have to be included in other genera by future studies. Although we did not sequence Helix christinae, the type species of Laeocathaica, our result shows a single clade supported by BPP/bootstrap value 99/68 that includes all species considered belonging to this group. Thus, we hypothesize for the time being that this is the correct Laeocathaica clade.
The indigenous dart-sac-bearing camaenids aggregated in Central China, which are grouped into the genera "Pseudobuliminus", "Buliminidius", "Bradybaena", "Cathaica", "Stilpnodiscus", "Pseudiberus", and Laeocathaica, could form a strongly supported monophyletic Clade F (Fig. 51), in which the members of each of the first five genera cannot be grouped together and the branch "Pseudiberus" is not represented by the type species. The present phylogeny (Fig. 51) shows the following five points:

Discussion
More than 200 species belonging to 28 genera were recorded as bradybaenine or believed to be dart-sac-bearing camaenids in Chinese Mainland Schileyko 2004;Wu 2004;Chen and Zhang 2004;Wu 2019;Zhang et al. 2019;Wu et al. 2019a;Wu et al. 2019b). This work confirms that the distribution range of the least known genus Laeocathaica is limited to W Hubei, Chongqing, Sichuan, S Gansu, and W Shaanxi and does not extend to other adjacent regions, as shown in Fig. 2A. In this area, Laeocathaica carinifera, mainly active in artificial environments, occupies the largest habitat (~ 76,500 km 2 , Fig. 2C) and seems to be the most successful species there. A previous work suggested that the parallel mountains situated at eastern Sichuan provided a series of relatively stable intermountainous environments in which populations of Laeocathaica carinifera (= L. subsimilis in Wu and Chen 1998) exhibited divergent shell morphology, reflecting microevolution in relatively isolated environments (Wu and Chen 1998). In contrast, most other congeners of Laeocathaica carinifera show a pattern of much narrower distribution. The South Gansu Plateau, a narrow region in northern Sichuan and the southern corner of Gansu, has nineteen Laeocathaica species that largely geographically overlap. Each species usually occupies only one or a few small areas, for extreme examples ~ 10 km 2 for Laeocathaica phaeomphala and ~ 100 km 2 for L. potanini (Fig. 3), which are much more endemic in the limited local environment than for some other camaenids (e.g., Exiligada, Criscione et al. 2012). The variously conditioned rugged terrain of mountains and intermountainous valleys with multiple species make this region a hotspot for land snails, where the malacodiversity in this region is approximately 30 times richer than that in the rest territory of China (Wu and Xu 2013;Wu 2018).
The work of Páll-Gergely et al. (2022), in which all species in the genus Laeocathaica were revised, has served as an essential basis for the present study. Laeocathaica stenochone, treated by Páll-Gergely et al. (2022) as a synonym of L. carinifera based on conchological characteristics, has a much denser granulation on the embryonic shell, a higher relative shell height, and differently structured genital organ compared to the latter. The phylogram based on partial 16S and partial ITS2 data could indicate that the branch ((Laeocathaica stenochone HBUMM08431 + L. carinifera HBUMM05103) + L. carinifera HBUMM05131) represents a single species or two species if the problem identified by Will et al. is taken into account   fig. 1) for species identification using the barcode protocol. The sequence data of HBUMM08431, HBUMM05103, and HBUMM05131 share the same ITS2 sequence and only differ in three sites on the 16S gene. Therefore, the present phylogenetic analyses on these three samples are identical to those obtained by a traditional barcoding method for identifying species. In the present work we therefore prefer to treat Laeocathaica stenochone and L. carinifera as two species, since they are morphologically distinguishable. Nevertheless, the present phylogram suggests that Laeocathaica carinifera has a deep phylogenetic affinity to L. stenochone.
Until now, the systematic position of Laeocathaica remained an open question. Before this work, one of the two studies on the systematic position of Laeocathaica was based on a morphological character-based phylogram, in which Laeocathaica carinifera (= L. subsimilis, L. filippina in Wu 2004) is deeply embedded and receives very weak non-homoplasious support based on that dataset (Wu 2004). Based on partial mitochondrial 16S and CO1 sequences, another work involving Laeocathaica polytyla and L. distinguenda provided phylograms which both indicate that Laeocathaica shares the same robustly supported branch with Acusta Martens, 1860 and Pseudobuliminus Gredler, 1886 (Chen et al. 2021). In this second work, the monophyly of Laeocathaica was questioned because Laeocathaica polytyla is close to Acusta and Pseudobuliminus instead of close to L. distinguenda, which does not agree with our work, where the Laeocathaica is possibly monophyletic, when more congeners (i.e., 13 Laeocathaica species) join the analyses based on the combined ITS2 and 16S dataset (Fig. 51).
The present phylogenetic inference is consistent with the phylogram of Wade et al. (2007), since Satsuma A. Adams, 1868 andNesiohelix Kuroda &Emura, 1943 are basal on the phylogram, reflecting the evolutionary relationships of eastern Asian camaenids. The camaenine ingroup genus Satsuma, which agrees regarding its basal location on phylogram with some authors (Chiba 1999;Wade et al. 2007;Chen et al. 2021), shows a minute difference between Nesiohelix and Traumatophora Ancey, 1887 in the sequences of 16S rDNA and ITS2. The presence of a flagellum only on basal clades, represented by Nesiohelix, Satsuma, Camaenella, Traumatophora, Aegista Albers, 1860, and Plectotropis Martens, 1860, which are representatives of SE Chinese Mainland, Taiwan, Hainan, and Japan (Pfeiffer 1865;Azuma 1982;Zhou et al. 2011;Wu and Asami 2017;Wu 2019) and clearly diverge from those genera distributed in Central China (Möllendorff 1899;Chen and Zhang 2004;Wu and Prozorova 2006), agrees with that the presence or absence of the flagellum can be used as a character state coding for higher-level classification (Hirano et al. 2014;Jirapatrasilp et al. 2022). The positions of Nesiohelix, Aegista, Acusta, and Bradybaena Beck, 1837 (represented by Bradybaena spp. on Clade D, Fig. 51), from the basal part to the upper part, correspond topologically to the phylogenies of Wade et al. (2007). Comparing the basal part, the taxa on Clade F (Fig. 51) could present a highly evolved and diverse group among the East Asian camaenids. However, the present phylogenetic analyses suggest that Pseudobuliminus, Buliminidius, Bradybaena, Cathaica, and Stilpnodiscus are polyphyletic and an intensive revision is required.
Clade F (Fig. 51), which roughly corresponds to the clade containing Acusta, Laeocathaica, Pseudobuliminus,and Bradybaena in the phylogram proposed by Chen et al. (2021), is characterized by the presence of a penial sheath and a dart sac, and the absence of an epiphallic papilla, a penial caecum, or a flagellum. On Clade F, the proximal accessory sac is widely present in different subclades including Stilpnodiscus moellendorffi (Wu 2001: fig. 4A, E;Wu 2004: fig. 16A, C), "Cathaica" pulveratricula (Fig. 52B), Laeocathaica spp. (text figures listed below most species in this study; Fig. 52C, E, F), and "Stilpnodiscus" entochilus (Wu 2004: fig. 16D, E). On Clade C, the proximal accessory sac is also present in Cathaica fasciola. However, the structures of the terminal genitalia including the proximal accessory sac of the taxa on Clade C are divergent. In C. fasciola there are two small proximal accessory sacs attaching at both lateral-ventral sides of the dart sac (Fig. 52A) while in "Cathaica" pulveratricula there is a single proximal accessory sac on the left side of dart sac (Fig. 52B). However, in both Cathaica species the accessory sac is absent and the mucous glands open into dart sac chamber (Fig. 52A, B) in contrast to all examined Laeocathaica species, where the accessory sac is present and the mucous glands open into the dart chamber via an accessory sac (Fig. 52C, E, F). The frequent occurrence of a proximal accessory sac in the subclades of Clade C indicates this structure might be one of the most valuable characters and deserving of detailed examination in respect of taxonomy and evolution in the dart-sac-bearing camaenids. Figure 52. Schematics of terminal genitalia of some dart-sac-bearing camaenids A Cathaica fasciola (Draparnaud, 1801) (stylized pattern from HBUMM8142-spec. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]9 fma;Qingyang,Gansu,35.738°N,107.701°E, 1353 m a.s.l.; coll. Sheng, X.-F., 2017-VII) B "Cathaica" pulveratricula (Martens, 1882) (stylized pattern from HBUMM08208), one proximal accessory sac is present at the left side of dart sac C Laeocathaica spp. with two proximal accessory sacs at both sides of dart sac D L. phaeomphala Möllendorff, 1899, without proximal accessory sac and with elongated vagina above dart sac E L. amdoana Möllendorff, 1899, with two tiny proximal accessory sacs and with elongated vagina above dart sac F L. dolani , with a proximal accessory sac at the right side of dart sac. Notes: any fleshy septum inside dart sac chamber is not shown; red dots indicate openings of proximal accessory sac. Abbreviations: ASaccessory sac; DS -dart sac; DSC -dart sac chamber; DtC -a chamber containing love dart; MG -mucous glands; PAS -proximal accessory sac; PR -penial retractor muscle; PS -penial sheath; Va -vagina.