Integrative taxonomic revision of the land snail genus Sarika Godwin-Austen, 1907 in Thailand, with descriptions of nine new species (Eupulmonata, Ariophantidae)

Abstract Members of the land snail genus SarikaGodwin-Austen 1907 are superficially similar and difficult to differentiate by their shell morphology so that their species limits are still unclear. In order to resolve the taxonomy of this group, a phylogenetic reconstruction of Sarika is presented, based on morphological and anatomical characters, as well as on partial sequences of the mitochondrial cytochrome c oxidase subunit I (COI) gene. In total, 23 species of Sarika are recognised in Thailand, and nine species are new to science, namely S. caligina Pholyotha & Panha, sp. nov., S. gratesi Pholyotha & Panha, sp. nov., S. inferospira Pholyotha & Panha, sp. nov., S. lactospira Pholyotha & Panha, sp. nov., S. megalogyne Pholyotha & Panha, sp. nov., S. melanospira Pholyotha & Panha, sp. nov., S. pellosa Pholyotha & Panha, sp. nov., S. solemi Pholyotha & Panha, sp. nov., and S. subheptagyra Pholyotha & Panha, sp. nov. Results from genital examination and COI analyses confirm the monophyly of Sarika and its species. The intra- and inter-specific genetic distances of Sarika were 0–3.7% and 4.6–12.0%, respectively. Colour images of the living adults, shell, and genitalia along with SEM images of the spermatophore and radula are given. In addition, an identification key and a geographical distribution map of Sarika species are provided.


Introduction
Thailand contains a high diversity of land snails and high levels of species endemism, which is likely due to its position in the centre of the zoogeographical regions of Indo-Burma and Sundaland, a large extensive range of several limestone and mountainous hills, various kinds of tropical forests, and a high relative humidity (Myers et al. 2000;Gupta 2005;Clements et al. 2006;Naggs et al. 2006;Ridd et al. 2011;Gardner et al. 2015). To date, many groups of land snails in Thailand have been well studied, such as micro-snails (e.g., Tongkerd et al. 2004), the colourful tree snails (e.g., Sutcharit and Panha 2006), carnivorous snails (e.g., Siriboon et al. 2014), and operculate snails (e.g., Nantarat et al. 2014). However, information on the common ground-dwelling land snail genus Sarika Godwin-Austen, 1907 is very scanty, so that the taxonomic status of most Sarika species is still doubtful and needs to be resolved.
Subsequentially, many species have been placed in the genus Sarika (Laidlaw 1933;Solem 1966;Panha 1996;Hemmen and Hemmen 2001;Pholyotha et al. 2018Pholyotha et al. , 2020aPholyotha et al. , 2020cInkhavilay et al. 2019). Yet, most previous studies were either species descriptions or checklist, and in Thailand and Malaysia, only a few studies so far have dealt with the genital anatomy (Godwin-Austen 1907;Laidlaw 1933;Solem 1966;Maneevong 2000;Sutcharit and Panha 2008). In Laos, Inkhavilay et al. (2019) published a checklist of the land snails, including several species of Sarika. A year later, the genus Sarika from Myanmar and Cambodia were taxonomically revised, and two new species from Myanmar and three new species from Cambodia were discovered based on genitalia characters (Pholyotha et al. 2020a(Pholyotha et al. , 2020cSutcharit et al. 2020). However, knowledge on the genus Sarika is still fragmentary because most of the nominal species are described from Thailand. Therefore, we examined the anatomy of specimens collected during intensive field surveys throughout Thailand, and found that the diversity of this genus remains underestimated and its complex relationships are a mystery. This present study is the first comprehensive taxonomic treatment of the land snail genus Sarika based on conchological and anatomical characters and data on the mitochondrial cytochrome c oxidase subunit I (COI) gene. The COI gene has been widely used to resolve the phylogenetic relationships among closely related species in several land snails (Liew et al. 2009;Nantarat et al. 2014;Köhler and Criscione 2015;Hyman and Köhler 2018). Thus, we analysed the COI gene phylogeny of Sarika to test the monophyly of each species and to understand the phylogenetic relationships of Sarika. This work includes taxonomic updates, illustrations of type specimens (when possible), and descriptions of the living snails, shells, genitalia, radula, and spermatophore. Moreover, nine Sarika species are herein described as new to science. An identification key to Sarika is provided and the distribution ranges for species are updated.

Specimen sampling and morphological studies
This work is based on new specimens collected throughout Thailand and voucher specimens deposited in the Chulalongkorn University Museum of Zoology (CUMZ), Bangkok. Living specimens were photographed, euthanised by two-step methods (American Veterinary Medical Association 2020), and then fixed in 95% (v/v) ethanol for morphological and DNA studies. Species identification followed the original descriptions by Godwin-Austen (1907), Blanford and Godwin-Austen (1908) and Pholyotha et al. (2020c), and were then compared to the relevant type specimens. To study anatomy, 3-10 specimens of each species were dissected and examined under a stereomicroscope. Adult shells were used to measure the shell height and shell width, and to count the number of whorls. Shells and genitalia were imaged using a digital camera and a stereomicroscope with Cell'D Imaging Software. Radulae were extracted, soaked in 10% (w/v) sodium hydroxide, cleaned with distilled water, and then imaged by scanning electron microscopy (SEM; JEOL, JSM-6610 LV).
In the material examined sections, shells refer to empty shells while specimens refer to specimens preserved in ethanol. The Thai terms "Tham" meaning cave, "Wat" meaning temple, and "Phu" and "Khao" for mountain or hill are used throughout for the locality names.
Descriptions of all new species herein are attributed to Pholyotha & Panha.

COI analyses
Details of samples selected for COI analysis are shown in Table 1. DNA was extracted from the foot muscle using the NucleoSpin Tissue Kit (Macherey-Nagel, Germany), following the standard procedure of the manufacturer. A fragment of the mitochondrial cytochrome c oxidase subunit I (COI) gene was amplified from each specimen by PCR using the universal primer pair LCO1491 (5′-GGTCAACAAATCATAAAGATATTGG-3′) and HCO2198 (5′-TAAACTTCAGGGTGACCAAAAAATCA-3′) (Folmer et al. 1994).
The reaction was performed using standard protocols (Nantarat et al. 2014) with annealing temperatures of 50 °C or 52 °C for 120 s. The amplified PCR products were checked under an UV transilluminator after gel electrophoresis, then commercially sequenced by Bioneer Co., Korea, with the same primers in both directions. Nucleotide sequences were deposited in GenBank under accession numbers: MT894062-MT894119 (see Table 1). The COI gene sequences were edited and aligned using ClustalW, as implemented in the MEGA7 software (Kumar et al. 2016). Genetic distances between Sarika species and related taxa were calculated using Kimura's two-parameter model (K2P) as implemented in MEGA7 (Kumar et al. 2016). The alignments were tested for substitution saturation using DAMBE (Xia 2013). As no saturation was detected in the sequences (Iss < Iss.c with p < 0.01), all the codon positions were used in the subsequent analysis. The phylogenetic analyses were conducted using maximum likelihood (ML) and Bayesian inference (BI) and both analyses were performed on-line through the CIPRES Science Gateway (Miller et al. 2010). The ML analyses were performed by using the program RAxML-HPC2 on XSEDE v. 8.2.12 (Stamatakis 2014) with 1000 bootstrap replicates using GTRGAMMA as the model. Prior to the BI analysis, Kakusan4 (Tanabe 2011) identified the best-fit model as follows: the general time reversible model (Tavaré 1986) with gamma distribution for the first and the second COI codon positions, and the HKY model (Hasegawa et al. 1985) for the third COI codon position. The BI analysis was performed by using the program MrBayes on XSEDE v. 3.2.7a (Ronquist et al. 2012) with two simultaneous runs. The analysis was run for 10 million generations (default heating parameter), sampled every 500 generations, starting with a random tree and burn-in set to 50%. Convergence of the two runs was achieved if the average standard deviation of split frequencies were ≤ 0.01 (Ronquist et al. 2012). Bootstrap support values (BS) of ≥ 70% and BI posterior probabilities (PP) of ≥ 0.95 were regarded as significant (Hillis and Bull 1993;Felsenstein 2004;Huelsenbeck and Rannala 2004;Mauro and Agorreta 2010;Hirano et al. 2018).

Anatomical abbreviations
In the descriptions of the genitalia, the term 'proximal' refers to the region closest to the genital opening, while 'distal' refers to the region furthest away from the genital opening. The following abbreviations were used as defined by Godwin-Austen (1907), Blanford and Godwin-Austen (1908), Solem (1966), Sutcharit and Panha (2008), and Pholyotha et al. (2018Pholyotha et al. ( , 2020b

COI analyses
The partial COI gene sequence data set included 61 specimens of Sarika as well as eleven sequences from Macrochlamys, Taphrenalla Panha, 2020 andHemiplecta Albers, 1850, which were included as outgroups. The alignment of the COI gene fragments had a length of 655 base pairs. The obtained phylogenetic tree ( Fig. 1) recovered 17 species of Sarika forming a well-supported clade, including the type species S. resplendens and eight new species with high support (BS = 93%, PP = 1). Even though the phylogenetic relationships among taxa were poorly resolved, the members of Sarika were always retrieved as a monophyletic clade. A clade of Sarika appears as a sister group of Macrochlamys + Taphrenalla. Together Sarika + Taphrenalla + Macrochlamys formed a well-supported clade (BS = 100%, PP = 1). The mean genetic distances of the COI gene observed among Sarika, Taphrenalla, Macrochlamys, and Hemiplecta ranged from 9.8% (Taphrenalla and Macrochlamys) to 13.7% (Sarika and Hemiplecta). Intraspecies divergences within the genus Sarika ranged from 0% (S. bocourti) to 3.7% (S. dugasti), and interspecies divergences ranged from 4.6% (S. bocourti and S. inferospira sp. nov.) to 12.0% (S. dugasti and S. limbata), respectively (Table 2).
Genitalia with penial retractor muscle attached to tip of epiphallic caecum; penis generally without penial verge, except for S. consepta (Benson, 1860) and S. nana Pholyotha & Panha, 2020(see Pholyotha et al. 2020a, 2020c, rarely present pseudoverge; flagellum short to long; gametolytic duct long; dart apparatus large cylindrical. Spermatophore long and needle-shaped with three recognizable sections: (i) head filament rather short, (ii) cylindrical sperm sac containing sperm mass, and (iii) tail filament long thick walled tube with small hole in cross section and several spines present. Radular teeth with symmetrical tricuspid central tooth, asymmetrical tricuspid lateral teeth, and bicuspid marginal teeth.
Species of Sarika with well-developed mantle edge (mantle lobe) with four lobes (one shell lobe and three dorsal lobes) or five lobes (two shell lobes and three dorsal lobes); sole tripartite, lateral foot margin, caudal foss, and caudal horn present. Remarks. All species of Sarika whose genital anatomy is known have a straight (un-coiled) epiphallic caecum and can be divided into three species groups. This informal subdivision is based on the number of mantle lobes, structure of genitalia and spermatophore (when available). It may be helpful as an alternative aid to identification.
Group III: Sarika dugasti group. Has five mantle lobes as in group I, penis with pseudo-verge (Fig. 3D), which probably originates from an invagination of the penial wall to become a large papilla (penial verge like). Unfortunately, no information about the spermatophore. This group comprises two species: S. dugasti and S. solemi sp. nov.

Key to species of the genus Sarika Godwin-Austen, 1907 in Thailand
This identification key is mainly based on the characters of genitalia and spermatophores, and is based on some taxonomic informative characters of shells.

17
Snail has conspicuous dark spiral band at body whorl below suture (Fig. 33E); flagellum much smaller than epiphallus (Fig. 39C)  three spines and terminal part more than ca. one-third of its length with series of several branching spines.
Description. Shell. Shell comparatively depressed, large size (shell width up to 23.4 mm, shell height up to 11.5 mm), and rather thin. Shell surface smooth and glossy; shell colour pale brown. Whorls 5½-6½, increasing regularly; body whorl large and well rounded. Spire slightly to moderately elevated; suture impressed. Aperture crescent-shaped and obliquely opened. Peristome simple. Columellar margin simple and little reflected near umbilicus. Umbilicus narrowly opened (Fig. 11A, B).
Genital organs. Atrium short. Penis cylindrical with thin penial sheath covering proximal penis. Inner sculpture of penis fully covered with cuboidal penial pilasters of variable sizes; proximal area near atrium with very fine longitudinal pilasters then transformed to small pilasters; middle of chamber pilasters much larger than others; distal pilasters reduced to small pilasters. Epiphallus cylindrical, slightly narrower than penis and approximately as long as penis. Epiphallic caecum short, straight, same diameter as proximal epiphallus and located near middle of epiphallus. Penial retractor muscle large, thickened and attached at tip of epiphallic caecum. Flagellum long and slender tube, approximately half of epiphallus length. Vas deferens thin tube connecting distal epiphallus and free oviduct (Fig. 12).
Vagina cylindrical and short approximately one-third of penis length. Dart apparatus large, long cylindrical, and located on atrium at vagina and penis junction. Gametolytic sac bulbous ( Fig. 12C with spermatophore); gametolytic duct long and cylindrical. Free oviduct cylindrical, longer than vagina and proximal end encircled with thick tissue (Fig. 12A, C).
Spermatophore long and needle-shaped. Sperm sac enlarged and elongate-oval. Head filament gourd shape with irregularly obtuse-serrate longitudinal ridges. Tail filament very long tube; region near sperm sac with three spines. Spine I located on same base with spine II, simple, short and little curved. Spine II large and long, branching into many spinules near the tip. Spine III shorter than spine II and with complicated branching into small and many spinules. Region furthest away smooth and without spine; terminal part (more than ca. one-third of its length) with series of short to long branching spines that arranged in a row or encircled tail filament tip (Fig. 13).
External features. Animal with reticulated skin, dark grey body and dorsally with darker colour than below and foot sole. Caudal foss present; caudal horn raised and rather large. Mantle edge well developed, same colour as body, and with two shell lobes and three dorsal lobes. Shell lobes elongate; right shell lobe larger and longer than left shell lobe. Dorsal lobes large and broad; anterior left dorsal lobe and posterior left dorsal lobe (post-ldl) smaller than right dorsal lobe ( Fig. 9A-C).
Distribution. Sarika resplendens occurs throughout Thailand (Fig. 5) and mainland Southeast Asia (Schileyko 2011;Inkhavilay et al. 2019). This species can be found throughout the entire year in various humid areas in both natural and highly disturbed habitats. It is very easy to find and is the most common Sarika species in humanmodified habitats such as plant farms or shaded gardens. COI analysis. The ML and BI analyses revealed that the individuals of S. resplendens (n = 7) form a monophyletic group with high support ( Fig. 1; BS = 93%, PP = 1). The mean intraspecific genetic distance of S. resplendens was 1.8% (Table 2). Remarks. The type specimen of this species could not be located, only the specimens recognised by Godwin-Austen (1898, 1907 were examined. Sarika resplendens was examined in both shell and genitalia by Godwin Austen (1898,1907), whose specimens were collected from Mergui [topotype] and sent by Theobald. In this study, we examined specimens from Mergui (Theobald collection) deposited in the NHM collections. Genitalia of these historical specimens and the new specimens from Thailand were identical in having a large penial retractor muscle and cuboidal shape of penial pilasters sculpture. In addition, the terminal part of the spermatophore tail filament had a cluster of branching spines. This character was not described or mentioned in Godwin Austen (1898,1907). ( Diagnosis. Shell large to very large, depressed to conoid-depressed and rounded to slightly obtusely angulated body whorl. Animal with pale grey body and five mantle lobes. Genitalia with straight epiphallic caecum and small cuboidal penial pilasters. Spermatophore: head filament with irregularly smooth longitudinal ridges; tail filament near sperm sac with two spines and terminal part more than ca. one-eighth of its length with series of several branching spines.

Sarika dohrniana
Description. Shell. Shell depressed to conoid-depressed, large to very large size (shell width up to 33.2 mm, shell height up to 18.9 mm) and rather thin to slightly solid. Shell surface smooth, rather coarse above periphery; shell colour yellowish brown to dark brown. Whorls 6-6½, increasing regularly; body whorl large and rounded to slightly obtusely angulated. Spire very much elevated; suture impressed. Aperture crescent-shaped and obliquely opened. Peristome simple. Columellar margin simple and slightly reflected near umbilicus. Umbilicus narrowly opened (Fig. 11C, D).
Genital organs. Atrium short. Penis cylindrical, elongate and with thin penial sheath covering proximal penis. Inner sculpture of penis proximally more than ca. half of penial chamber with very fine longitudinal penial pilasters, and then transformed to small cuboidal pilasters. Epiphallus cylindrical, as long as penis and slightly narrower than penis. Epiphallic caecum short, straight, approximately same diameter as epiphallus, and located near middle of epiphallus. Penial retractor muscle thin and attached at tip of epiphallic caecum. Flagellum slender and long, approximately as long as epiphallus. Vas deferens thin tube connecting distal epiphallus and free oviduct (Fig. 14A, B).
Vagina cylindrical and approximately half of penis length. Dart apparatus enlarged, long cylindrical, and located on atrium at vagina and penis junction. Gametolytic sac bulbous; gametolytic duct long and cylindrical. Free oviduct short, approximately half of vagina length, and proximal end encircled with thick tissue (Fig. 14A).
Spermatophore long and needle-shaped. Sperm sac enlarged and elongate-oval. Head filament gourd shape with irregularly smooth longitudinal ridges. Tail filament very long tube; region near sperm sac with two spines. Spine I simple and little curved. Spine II long and branching into many spinules near the tip. Most of region furthest away smooth and without spine; terminal part (more than ca. one-eighth of its length) with series of short to long branching spines arranged in opposite rows (Fig. 15).
External features. Animal with reticulated skin and pale grey body, dark creamy mixing with grey foot sole and dark creamy to pale grey caudal horn. Mantle edge well developed and same colour as body (Fig. 9D). Distribution. Sarika dohrniana occurs in the karstic habitats and forested mountains in northeastern and central Thailand (Fig. 6).
COI analysis. The ML and BI analyses of S. dohrniana revealed that three individuals formed a monophyletic group with very strong support ( Fig. 1; BS = 100%, PP = 1), sister to the rest of most species of Sarika, except for S. solemi sp. nov. + S. dugasti. The mean intraspecific genetic distance of S. dohrniana was 1.7% (Table 2).
Remarks. The remarkable characters of S. dohrniana are its large size, conoiddepressed shell, the coarser shell surface compared to other Sarika species, and the head filament of the spermatophore with its irregularly smooth longitudinal ridges and the two spines on the tail filament near the sperm sac.  Diagnosis. Shell medium to large, depressed and well rounded body whorl. Animal with greyish to slightly dark grey body and five mantle lobes. Genitalia with straight epiphallic caecum and triangular prism penial pilasters. Spermatophore: head filament with irregularly obtuse-serrate longitudinal ridges; tail filament near sperm sac with three spines and terminal part more than ca. one-third of its length with series of several branching spines.
Description. The unique shell characters of S. obesior are depressed, medium to large size (shell width up to 22.1 mm; shell height up to 11.3 mm), pale brown, wellrounded body whorl, spire elevated, and impressed suture (Fig. 11E, F).
The unique genitalia characters are straight epiphallic caecum; inner wall of penis with very fine longitudinal penial pilasters near atrium, changing to large rhomboid pilasters with acute angle on top (triangular prism shape) (Fig. 14C, D).
Spermatophore long and needle-shaped. Sperm sac (ss) enlarged and elliptical. Head filament gourd shape with irregularly obtuse-serrate longitudinal ridges. Tail filament very long tube; region near sperm sac with three spines. Spine I located near base of spine II, simple and short. Spine II broken. Spine III large with complicated branching into small and many spinules. Region furthest away smooth and without spine; terminal part (more than ca. one-third of its length) with series of short to long branching spines arranged in a row or encircling the tail filament tip (Fig. 16).
Living snail with monochrome greyish to slightly dark grey body. Mantle edge well developed and same colour same body (Fig. 9E).
COI analysis. The ML and BI analyses showed that the individuals of S. obesior (n = 4) formed a monophyletic group with high support ( Fig. 1; BS = 98%, PP = 1). The mean intraspecific genetic distance of S. obesior was 3.0% (Table 2).
Remarks. This species has recently been re-described and illustrated based on the samples collected from Myeik, Myanmar by Pholyotha et al. (2020c). The topotypic specimens from Petchaburi, Thailand agree well with the previous descriptions. Solem (1966) noted that S. obesior differs from S. hainesi in having a rounded body whorl and attributed several specimens from northern and eastern Thailand to S. obesior. Yet, without the genital anatomy their identification could not be confirmed. Therefore, the specimens from northern and eastern Thailand as reported by Solem (1966) are still doubtful, and to date, the distribution of S. obesior is probably restricted to western and southern Thailand and south-eastern Myanmar.  Diagnosis. Shell large, depressed and well-rounded body whorl. Animal with pale to dark grey body and five mantle lobes. Genitalia with straight epiphallic caecum and inner penial sculpture with small reticulated pilasters in proximal part and small cuboidal pilasters in distal end. Spermatophore: head filament with irregularly platelike sculpture; tail filament near sperm sac with three spines and terminal part more than ca. one-third of its length with series of several branching spines.
Genital organs. Atrium short. Penis cylindrical with thin penial sheath covering proximal penis. Inner sculpture of penis proximally more than ca. one-fifth of penial chamber covered with very fine longitudinal penial pilasters, changing to small and thin reticulated pilasters around two-fifth of chamber, and transformed to small cuboidal pilasters at distal end near epiphallus. Epiphallus cylindrical, approximately two times total penis length, and smaller diameter than penis. Epiphallic caecum short, straight, similar diameter as proximal epiphallus, and located near middle of epiphallus. Penial retractor muscle thin and attached at tip of epiphallic caecum. Flagellum very slender, and approximately same length as penis. Vas deferens thin tube connecting distal epiphallus and free oviduct (Fig. 18A, B).
Vagina cylindrical and ca. two-thirds penis length. Dart apparatus large, long, cylindrical, and located on atrium of vagina and penis junction. Gametolytic sac enlarged and bulbous; gametolytic duct long and cylindrical. Free oviduct cylindrical, approximately same length with penis, and proximal end encircled with thick tissue (Fig. 18A).
Spermatophore long and needle-shaped. Sperm sac enlarged and elongate-oval. Head filament gourd shape; region close to sperm sac with irregularly plate-like sculpture then transformed to irregularly acute-serrate longitudinal ridges. Tail filament very long tube; region near sperm sac with three spines. Spine I very reduced to small knob. Spine II was broken but slightly large at base. Spine III (partially broken) with branching into small spines and spinules. Region furthest away smooth and without spine; terminal part (more than ca. one-third of its length) with series of short to long and complicated branching spines, arranged in a row or opposite rows near tail filament tip (Fig. 19).
External features. Animal with reticulated skin and pale to dark grey body, pale grey foot sole, and dark grey caudal horn. Mantle edge well developed and same colour as body (Fig. 9F).
Distribution. Sarika limbata occurs eastwards of the Tenasserim Range to the Phuket Range and is common in Chumphon Province (Fig. 7). COI analysis. The ML and BI analyses revealed that the samples of S. limbata (n = 4) formed a monophyletic group with very strong support ( Fig. 1; BS = 100%, PP = 1), and sister to S. lactospira sp. nov. with only BI support ( Fig. 1; PP = 0.99). The mean intraspecific genetic distance of S. limbata was 1.2% (Table 2).
Remarks. The shell morphology of S. limbata is similar to that of S. kawtaoensis. The main distinguishing characters of S. limbata are the reticulated and cuboidal penial pilasters, and the plate-like and acute-serrate longitudinal ridges on the head filament of the spermatophore. In contrast, S. kawtaoensis has reticulated and irregular large folded penial pilasters and acute-serrate longitudinal ridges on the head filament of the spermatophore.  Diagnosis. Shell large, strongly depressed and well-rounded to slightly shouldered body whorl. Animal with pale grey body and five mantle lobes. Genitalia with straight epiphallic caecum and cuboidal penial pilasters. Tail filament of spermatophore near sperm sac with three spines and terminal part of tail filament more than ca. one-fourth of its length with series of several branching spines.

Sarika heptagyra (Möllendorff, 1902)
Description. Shell. Shell strongly depressed, large size (shell width up to 27.9 mm, shell height up to 13.1 mm) and rather thin. Shell surface smooth and glossy; shell colour pale yellowish brown to very pale brown. Whorls 6-7, increasing regularly; body whorl large, rounded to slightly shouldered. Spire slightly elevated; suture rather impressed. Aperture crescent-shaped and obliquely opened. Peristome simple. Columellar margin simple and slightly reflected near umbilicus. Umbilicus narrowly opened (Fig. 17D-F).
Genital organs. Atrium short. Penis cylindrical with thin penial sheath covering proximal penis. Inner sculpture of penis proximally more than ca. one-third of penial chamber with fine longitudinal penial pilaster to nearly smooth surface, and then modified from small to large cuboidal pilasters arranged in oblique rows. Epiphallus cylindrical, approximately as long as penis but narrower than penis. Epiphallic caecum short, straight, same diameter as epiphallus, located near middle of epiphallus. Penial retractor muscle thin and attached at tip of epiphallic caecum. Flagellum slender, approximately as long as penis. Vas deferens thin tube connecting distal epiphallus and free oviduct (Fig. 18C, D).
Vagina cylindrical, ca. one-third of penis length. Dart apparatus large, long cylindrical, and located on atrium at vagina and penis junction. Gametolytic sac enlarged and bulbous; gametolytic duct long cylindrical. Free oviduct cylindrical, nearly two times of vagina length, and proximal end encircled with thick tissue (Fig. 18C). Spermatophore long and needle-shaped. Sperm sac enlarged and elongate-oval. Head filament was missing (incomplete spermatophore). Tail filament very long tube; region near sperm sac with three spines. Spine I simple, curved, and short. Spine II large and long, and branching part was missing. Spine III short and smaller than spine II, and branching part was missing. Region furthest away smooth and without spine; terminal part (more than ca. one-fourth of its length) with a series of short to long branching spines arranged in a row or encircled tail filament tip (Fig. 20). Radula. Teeth with half row formula: 1-(11-12)-63. Central tooth symmetrical tricuspid; lateral teeth asymmetrical tricuspid; marginal teeth elongate bicuspid. Marginal teeth starting at approximately row number 11 or 12 (Fig. 30E).
External features. Animal with reticulated skin and pale grey body, dark creamy mixing with grey foot sole and slightly dark grey caudal horn. Mantle edge well developed and same colour as body (Fig. 10A).
Distribution. This species is known from the limestone outcrops in Kanchanaburi Province (Fig. 6). COI analysis. The ML and BI analyses showed that the specimens of S. heptagyra (n = 3) formed a monophyletic group with very strong support ( Fig. 1; BS = 100%, PP = 1). The mean intraspecific genetic distance of S. heptagyra was 3.5% (Table 2).
Remarks. Sarika heptagyra is similar to S. resplendens. According to the phylogenetic tree, the relationship between S. heptagyra and S. resplendens is not clearly resolved (Fig. 1). The average interspecific sequence divergences between them were rather high at 7.7% which is in the recognised species range (4.6-12.0%) of interspecies sequence divergence of Sarika (see Table 2). Therefore, we have recognised S. heptagyra and S. resplendens as distinct biological species. The distinguishing character of S. heptagyra is its thin and long penial retractor muscle, while S. resplendens has very large and thickened penial retractor muscle (Table 2).
Sarika heptagyra seems to be indigenous in limestone habitats in western Thailand. Figure 16. Spermatophore of Sarika obesior specimen CUMZ 7678 A general view of the spermatophore B head filament C-E tail filament C three spines located close to the sperm sac D region with and without branching spines, and E branching spines on the tip region. Yellow arrowhead indicates the end of the spines from the tip.     Diagnosis. Shell large, depressed to globosely depressed and well-rounded body whorl. Animal with pale to dark grey body with five mantle lobes. Genitalia with a short straight epiphallic caecum. Inner penial sculpture with reticulated pilasters in proximal part and irregular surface folds arranged in oblique row at distal end. Spermatophore with irregularly acute-serrate longitudinal ridges on the head filament, tail filament with three spines, more than ca. half of its length with series of branching spines.

Sarika kawtaoensis
Description. Shell. Shell depressed to globosely depressed, large size (shell width up to 26.6 mm, shell height up to 15.2 mm), and rather thin. Shell surface smooth, polished; shell colour pale warm brown to medium brown. Whorls 6-7, increasing regularly; body whorl large and well rounded. Spire moderately to very much elevated; suture impressed. Aperture crescent-shaped and obliquely opened. Peristome simple. Columellar margin simple and slightly reflected near umbilicus. Umbilicus narrowly opened (Fig. 21A-D).
Genital organs. Atrium short. Penis cylindrical with thin penial sheath covering proximal penis. Inner sculpture of penis divided into three parts; proximally approximately one-third of penial chamber with very finely longitudinal penial pilasters to nearly smooth surface; middle approximately one-third of chamber covered with reticulated pilasters; distally approximately one-third pilaster transformed to irregular surface folds arranged in oblique row. Epiphallus cylindrical, approximately as long as penis and narrower penis. Epiphallic caecum short, straight, diameter slightly larger than epiphallus, and located near middle of epiphallus. Penial retractor muscle thin and attached at tip of epiphallic caecum. Flagellum long slender, approximately as long as epiphallus. Vas deferens thin tube connecting distal epiphallus and free oviduct (Fig. 22A, B).
Vagina cylindrical tube, approximately two-third of penis length. Dart apparatus large, long, cylindrical, and located on atrium at vagina and penis junction. Gametolytic sac bulbous; gametolytic duct long and cylindrical. Free oviduct cylindrical, almost as long as vagina and proximal end encircled with thick tissue (Fig. 22A).
Spermatophore long and needle-shaped. Sperm sac enlarged and elongate-oval. Head filament gourd shape with irregularly acute-serrate longitudinal ridges. Tail filament very long tube; region near sperm sac with three spines. Spine I simple, little curved, and short. Spine II large and long, branching into many spinules near the tip. Spine II almost the same size as spine II, with complicated branching into small spinules. Region furthest away smooth and without spine; terminal part (more than ca. half of its length) with series of long branching spines arranged in a row, and then transformed very long serrate-like spines arranged in opposite rows near the tail filament tip (Fig. 23).
External features. Animal with reticulated skin and pale to dark grey body, pale grey foot sole, and dark grey caudal horn. Mantle edge well developed and same colour as body (Fig. 10B).
Distribution. Sarika kawtaoensis is widely distributed throughout southern Thailand and occurs in both natural and populated community areas (Fig. 8). COI analysis. The ML and BI analyses of S. kawtaoensis revealed that the five individuals formed a monophyletic group with strong support ( Fig. 1; BS = 91%, PP = 1), sister to S. limbata + S. lactospira sp. nov. yet only with BI support ( Fig. 1; PP = 0.98). The mean intraspecific genetic distance of S. kawtaoensis was 3.3% (Table 2).
Remarks. Sarika kawtaoensis is a variable species in terms of shell shape ranging from nearly flattened (Fig. 21D) to a low-conical spire (Fig. 21A). The reproductive organs in these two shell morphs are identical. In addition, the DNA phylogeny also revealed that these shell variations grouped together with strong support within the clade of S. kawtaoensis (Fig. 1). Diagnosis. Shell large, depressed, and pale brown with well-rounded body whorl. Animal with blackish body and five mantle lobes. Genitalia with large, straight epiphallic caecum and triangular prism penial pilasters. Spermatophore: head filament with irregularly smooth longitudinal ridges; tail filament near sperm sac with three spines and terminal part of tail filament more than ca. half of its length with series of several branching spines.

Sarika caligina
Description. Shell. Shell depressed, large size (shell width up to 25.7 mm, shell height up to 12.3 mm), and thin. Surface smooth and polished; shell colour pale brown. Whorls 6-6½, increasing regularly; body whorl large and well rounded. Spire moderately elevated; suture impressed. Aperture crescent-shaped and obliquely opened. Peristome simple. Columellar margin simple and slightly reflected near umbilicus. Umbilicus narrowly opened (Fig. 21E, F).
Genital organs. Atrium short. Penis cylindrical with thin penial sheath covering proximal penis. Inner sculpture of penis proximally more than ca. two-third of penial chamber with very finely longitudinal penial pilasters to nearly smooth surface, and then gradually modified from small to large rhomboid pilasters with acute angle on top (triangular prism). Epiphallus cylindrical, slightly longer than penis. Epiphallic caecum large, straight and located proximally far from middle of epiphallus. Penial retractor muscle thin and attached at tip of epiphallic caecum. Flagellum long, slender and slightly longer than epiphallus. Vas deferens thin tube connecting distal epiphallus and free oviduct (Fig. 22C, D). Vagina cylindrical and approximately half of penis length. Dart apparatus large, long cylindrical, and located on atrium at vagina and penis junction. Gametolytic sac enlarged and bulbous; gametolytic duct enlarged and cylindrical (spermatophore inside). Free oviduct cylindrical, slightly shorter than total vagina length and proximal end encircled with thick tissue (Fig. 22C).
Spermatophore long and needle-shaped. Sperm sac enlarged and elongate-oval. Head filament gourd shape with irregularly smooth longitudinal ridges. Tail filament very long tube; region near sperm sac with three spines. Spine I simple, long, and slightly curved. Spine II large and long, branching into short spinules near the tip. Spine III shorter than spine II, branching into small and short spinules at the tip. Region furthest away smooth and without spine; terminal part (more than ca. half of its length) with series of short to long complicated branching spines arranged in a row or encircled the tail filament tip (Fig. 24).
External features. Animal with reticulated skin and very dark grey body. Foot sole and caudal foss present; caudal horn raised. Five mantle lobes well developed, same colour as body (Fig. 10C).
Etymology. The specific name caligina is from the Latin caliginis meaning mist, darkness and refers to the blackish colour of body, which characterises this species.
Distribution. Sarika caligina sp. nov. occurs in limestone habitats in central Thailand (Fig. 6). However, its habitats are threatened because many small karsts in this area have active quarries for the cement industry.
Remarks. This new species has a shell morphology that resembles S. resplendens, S. heptagyra, S. limbata and S. kawtaoensis. The distinguishing characters of this new species are its triangular prism-shaped penial pilasters, while S. resplendens and S. heptagyra have cuboidal penial pilasters, and S. limbata and S. kawtaoensis have reticulated penial pilasters. Moreover, S. caligina sp. nov. has irregularly smooth ridges on the head filament of the spermatophore, while S. resplendens has obtuseserrate ridges, S. limbata has plate-like and acute-serrate ridges, and S. kawtaoensis has acute-serrate ridges. Unfortunately, the head filament of S. heptagyra was not available for comparison.
Although S. caligina sp. nov. and S. obesior have a similar penial sculpture, the two species can be distinguished by their spermatophores. Sarika caligina sp. nov. has irregularly smooth ridges on the head filament and approximately half of the tail filament contains branching spines, whereas S. obesior has obtuse-serrate ridges on the head filament and approximately one-third of the tail filament contains branching spines.  Type locality. Wat Ao Sadet, Khanom, Nakhon Si Thammarat, Thailand, 9°17'20.9"N, 99°47'13.8"E.
Diagnosis. Shell large, depressed, pale yellowish brown with slightly shouldered body whorl and pale milky subsutural band. Animal with grey body and five mantle lobes. Genitalia with a straight epiphallic caecum and triangular prism pilasters on inner penial sculpture.
Description. Shell. Shell depressed, large size (shell width up to 23.6 mm, shell height up to 11.8 mm) and thin. Surface smooth and shiny; shell colour pale yellowish brown. Whorls 6-6½, increasing regularly; body whorl large and slightly shouldered. Spire moderately elevated; suture impressed and with narrow pale milky to whitish subsutural band. Aperture crescent-shaped and obliquely opened. Peristome simple. Columellar margin simple and slightly reflected near umbilicus. Umbilicus narrowly opened (Fig. 25A, B).
Genital organs. Atrium short. Penis cylindrical with thin penial sheath covering proximal penis. Inner sculpture of penis proximally more than ca. half of penial chamber with small longitudinal penial pilasters, and then gradually transformed from small to large rhomboid pilasters with acute angle on top (triangular prism). Epiphallus cylindrical and slightly shorter than twice the penis length. Epiphallic caecum long, straight, similar diameter with epiphallus and located proximally near middle of epiphallus. Penial retractor muscle thin and attached at tip of epiphallic caecum. Flagellum slender, approximately half length of epiphallus. Vas deferens thin tube connecting distal epiphallus and free oviduct (Fig. 26A, B).
Vagina cylindrical and approximately half of penis length. Dart apparatus large, long cylindrical, and located on atrium at vagina and penis junction. Gametolytic sac enlarged and bulbous; gametolytic duct long and enlarged (damaged spermatophore inside). Free oviduct large cylindrical, approximately as long as vagina length, and proximal end encircled with thick tissue (Fig. 26A).
External features. Animal with reticulated skin and body darker grey above and paler grey near foot sole. Caudal foss and caudal horn present. Five mantle lobes well developed and pale grey colour (Fig. 10D).
Etymology. The specific name lactospira is derived from the Latin words lacteus meaning milky and spira meaning coil. It refers to the pale milky colour below suture.
COI analysis. The ML and BI analyses revealed that the four individuals of S. lactospira sp. nov. formed a monophyletic group with very strong support ( Fig. 1; BS = 100%, PP = 1). The mean intraspecific genetic distance of S. lactospira sp. nov. was 2.3% (Table 2). Remarks. Sarika lactospira sp. nov. differs from all other species in the Sarika resplendens group by having a shouldered body whorl and usually with a narrow whitish subsutural band. In comparison the shell of S. lactospira sp. nov. has shouldered body whorl, while, S. resplendens, S. obesior, S. limbata, S. kawtaoensis, S. caligina sp. nov., and S. subheptagyra sp. nov. have a well-rounded body whorl, and S. dohrniana has a rounded to slightly obtusely angulated body whorl.
Compared among the shouldered body whorl species, the distinguishing character of S. lactospira sp. nov. is the triangular penial pilasters, while S. heptagyra has cuboidal penial pilasters.
Although S. lactospira sp. nov. and S. megalogyne sp. nov. have a similar shell and penial sculpture, the free oviduct and flagellum of S. lactospira sp. nov. are much shorter than those of S. megalogyne sp. nov. In addition, the COI sequence divergences between both species were rather high (7.1%). Unfortunately, the spermatophore of S. lactospira sp. nov. was not available for comparison. Diagnosis. Shell medium to large, depressed and very pale brown with wellrounded to slightly shouldered body whorl. Animal with grey body and five mantle lobes. Genitalia with a straight epiphallic caecum, very large free oviduct and triangular prism-shaped pilasters on inner penial sculpture. Spermatophore: tail filament near sperm sac with three spines and terminal part more than ca. three-quarters of its length with series of several branching spines. Description. Shell. Shell depressed, medium to large size (shell width up to 21.2 mm, shell height up to 11.3 mm), and thin. Surface smooth and glossy; shell colour very pale brown. Whorls 6-6½, increasing regularly; body whorl slightly well rounded to slightly shouldered. Spire moderately to very much elevated; suture impressed. Aperture crescent-shaped and obliquely opened. Peristome simple. Columellar margin simple and slightly reflected near umbilicus. Umbilicus narrowly opened (Fig. 25C, D).

Sarika megalogyne
Genital organs. Atrium short. Penis cylindrical with thin penial sheath covering proximal penis. Inner sculpture of penis proximally more than ca. one-third of penial chamber with very finely longitudinal penial pilasters to nearly smooth surface, and then gradually modified from small to large rhomboid pilasters with acute angle on top (triangular prism). Epiphallus cylindrical, slightly longer than penis length. Epiphallic caecum large, straight, diameter slightly larger than epiphallus, and located proximally near middle of epiphallus. Penial retractor muscle thin and attached at tip of epiphallic caecum. Flagellum long slender and slightly longer than epiphallus. Vas deferens thin tube connecting distal epiphallus and free oviduct (Fig. 26C, D).
Vagina cylindrical, enlarged and slightly shorter than penis. Dart apparatus large, long cylindrical, and located on atrium at vagina and penis junction. Gametolytic sac enlarged and bulbous; gametolytic duct long and cylindrical. Free oviduct enlarged cylindrical, extremely long, approximately three times of vagina length (Fig. 26C).
Spermatophore long and needle-shaped. Sperm sac and head filament were missing. Tail filament long tube; region near sperm sac with three spines. Spine I simple and short. Spine II large, long, and with complicated branching spines into spinules near the tip. Spine III smaller than spine II and with complicated branching spines into spinules. Region furthest away smooth and without spine; terminal part (approximately three-quarters of its length) with series of long complicated branching spines into spinules arranged in a row, and then transformed to very long serrate-like spines arranged in opposite rows near the tail filament tip (Fig. 27).
Radula. Teeth with half row formula: 1-(13-14)-55. Central tooth symmetrical tricuspid; lateral teeth asymmetrical tricuspid; marginal teeth elongate bicuspid. Marginal teeth starting at approximately row number 13 or 14 (Fig. 31D). External features. Animal with reticulated skin and body darker grey above and paler grey near foot sole. Caudal foss and caudal horn present. Five mantle lobes well developed and pale grey in colour (Fig. 10E).
Etymology. The specific name megalogyne is derived from the Greek word megale meaning large and the Greek gyne meaning female. It refers to the female part of genital organs with a very large free oviduct, which characterises this species. Distribution. Sarika megalogyne sp. nov. is common in Prachuap Khiri Khan and Chumphon provinces (Fig. 7). This species is often found under leaves of small trees and shrubs on limestones.
Remarks. Sarika megalogyne sp. nov. and S. caligina sp. nov. have similar genitalia and penial sculpture. However, S. megalogyne sp. nov. has a much longer free oviduct and flagellum than S. caligina sp. nov. In addition, the spermatophore of S. megalogyne sp. nov. with more than ca. three-quarters of the tail filament contains branching spines, whereas the spermatophore of S. caligina sp. nov. with more than ca. only half of the tail filament contains branching spines. Furthermore, the genetic distance between these two species is high (7.4%). Diagnosis. Shell large, strongly depressed and pale yellowish brown to pale brown with very rounded body whorl. Animal with grey body and five mantle lobes. Genitalia with a straight epiphallic caecum and triangular prism pilasters on inner penial sculpture. Spermatophore: head filament with irregularly smooth longitudinal ridges; tail filament near sperm sac with three spines and terminal part of tail filament more than more than ca. one-fourth of its length with series of branching spines.

Sarika subheptagyra
Description. Shell. Shell strongly depressed, large size (shell width up to 26.4 mm, shell height up to 12.4 mm), and thin. Surface smooth and glossy; shell colour pale yellowish brown to pale brown. Whorls 6-6½, increasing regularly; body whorl large and well rounded. Spire slightly elevated; suture impressed. Aperture crescent-shaped and opening obliquely. Peristome simple. Columellar margin simple and slightly reflected near umbilicus. Umbilicus narrowly opened (Fig. 25E, F).
Genital organs. Atrium short. Penis cylindrical with thin penial sheath covering proximal penis. Inner sculpture of penis proximally more than ca. one-third of penial chamber with very finely longitudinal penial pilasters to nearly smooth surface, and then gradually transformed from small to large rhomboid with acute angle on top (triangular prism). Epiphallus cylindrical, long and approximately one and half times as long as penis. Epiphallic caecum short, straight, and located proximally near middle of epiphallus, penial retractor muscle thin and attached at tip of epiphallic caecum. Flagellum long and slender, approximately as long as penis. Vas deferens thin tube connecting distal epiphallus and free oviduct (Fig. 28).
Vagina cylindrical and approximately as long as penis. Dart apparatus large, long cylindrical, located on atrium at vagina and penis junction. Gametolytic sac enlarged and bulbous; gametolytic duct long, cylindrical. Free oviduct cylindrical, longer than vagina and proximal end encircled with thick tissue (Fig. 28A).
Spermatophore long and needle-shaped. Sperm sac enlarged and elongate-oval. Head filament gourd shape with irregularly smooth longitudinal ridges. Tail filament very long tube; region near sperm sac with three spines. Spine I simple and rather short. Spine II large and long and branching into very small spinules. Spine III relatively smaller than spine II and branching into very small spinules. Region furthest away smooth and without spine; terminal part (more than ca. one-fourth of its length) with series of long branching spines into spinules arranged in a row, and then transformed to very long serrate-like spines arranged in opposite rows near the tail filament tip (Fig. 29).
External features. Animal with reticulated skin and pale to dark grey body. Foot sole and caudal foss present; caudal horn raised. Five mantle lobes well developed and same colour as body (Fig. 10F).
Etymology. The specific name subheptagyra is derived from the Latin word sub meaning under, from, somewhat, and less than, and the word heptagyra referring to shell similar to S. heptagyra.
Distribution. This species occurs only in Uthai Thani Province and is restricted to limestone habitats (Fig. 6).
Compared with S. resplendens, S. subheptagyra sp. nov. has a longer vagina and free oviduct, thin penial retractor muscle, and triangular prism-shaped penial pilasters. Sarika resplendens has a shorter vagina and free oviduct, a very large and thickened penial retractor muscle, and cuboidal-shaped penial pilasters. Additionally, the genetic distance between both species is fairly high (6.5%).
Sarika subheptagyra sp. nov. differs from S. caligina sp. nov. in having a lower spire, longer vagina, and free oviduct, and spine II and spine III on spermatophore start branching near the base, while S. caligina sp. nov. has a higher spire, shorter vagina and free oviduct, and spine II and spine III on spermatophore start branching near the tip. In addition, the genetic distance between these two new species is high (8.2%).  Diagnosis. Shell large, depressed, obtusely angulated body whorl. Animal with pale grey body and four mantle lobes. Genitalia with a large and straight epiphallic caecum, and a triangular prism shape of penial pilasters. Spermatophore with irregularly obtuse-serrate longitudinal ridges with numerous pores on the head filament, tail filament with two spines and more than ca. half of its length with series of long branching spines.

Group II: Sarika hainesi group: species without left shell lobe and without penial verge or pseudo-verge
Description. Shell. Shell depressed, large size (shell width up to 28.1 mm, shell height up to 14.9 mm) and rather thin. Shell surface smooth and polished; shell colour pale yellowish brown to pale brown. Whorls 6-7, size increasing regularly; body whorl large and obtusely angled. Spire moderately elevated; suture impressed. Aperture crescent-shaped and obliquely opened. Peristome simple. Columellar margin simple and slightly reflected near umbilicus. Umbilicus narrowly opened (Fig. 34A-C).
Genital organs. Atrium short. Penis cylindrical with thin penial sheath covering proximal penis. Inner sculpture of penis proximally more than ca. half of penial chamber with very finely longitudinal penial pilasters to nearly smooth surface, and then gradually transformed from small to large rhomboid pilasters with acute angle on top (triangular prism). Epiphallus cylindrical, approximately one and half times total penis length, and narrower than penis. Epiphallic caecum short, straight, same diameter as proximal epiphallus, and located near middle of epiphallus. Penial retractor muscle thin and attached at tip of epiphallic caecum. Flagellum long slender and almost as long as penis. Vas deferens thin tube connecting distal epiphallus and free oviduct (Fig. 35A, B).
Vagina cylindrical and slightly shorter than penis. Dart apparatus enlarged, long cylindrical and located on atrium at vagina and penis junction. Gametolytic sac enlarged and bulbous (with spermatophore inside); gametolytic duct long and cylindrical. Free oviduct cylindrical, approximately as long as vagina, and proximal end encircled with thick tissue (Fig. 35A).
Spermatophore long and needle-shaped. Sperm sac enlarged and elongate-oval. Head filament gourd shape and irregularly obtuse-serrate longitudinal ridges with numerous pores (sponge-like). Tail filament very long tube; region near sperm sac with two spines. Spine I located on same base with spine II, short and simple. Spine II large, long and very complicated branching into many spinules. Region furthest away smooth and without spine; terminal part (more than ca. half of its length) with series of long branching spines arranged in an arrow or encircled tail filament tip (Fig. 36).
External features. Animal with reticulated skin and pale grey body. Mantle edge well developed, pale grey, with one shell lobe, and three dorsal lobes. Dorsal lobes large and broad; anterior and posterior left dorsal lobes smaller than right dorsal lobe. Right shell lobe large and long and left shell lobe absent (Fig. 33B).
Distribution. This species is known only from the Dong Phaya Yen and Sankamphaeng Ranges in Saraburi and Nakhon Ratchasima provinces (Fig. 32). COI analysis. The ML and BI analyses revealed that the individuals of S. hainesi (n = 3) formed a monophyletic group with high support ( Fig. 1; BS = 96%, PP = 1). The mean intraspecific genetic distance of S. hainesi was 2.4% (Table 2).
Remarks. The type locality of S. hainesi was recorded simply as "Siam". Later, Pfeiffer (1856b: 76) stated that the described specimens were received from W.A. Haines. Although Haines had never visited Thailand, he described four land snail species from Thailand based on materials sent by the American physician S.R. House (Haines 1858: 157-158). We presumed that the Cuming ex. Haines specimen (syntype) was also received from S.R. House who lived in Bangkok from 1847-1876 (Feltus 1924). Therefore, the type locality of S. hainesi from central Thailand is the most likely. In addition, the specimen from central Thailand (S. hainesi s. s.) matched the syntypes in almost all the shell characters; however, the genitalia obviously differ from S. aff. hainesii sensu Solem (1966) from northern Thailand (Chiang Mai Province). We consider the northern Thailand populations as misidentified and propose them here as an undescribed species, S. solemi sp. nov. Moreover, the COI sequence divergences between S. hainesi and S. solemi sp. nov. are very high (10.2%). Sarika hainesi was first reported from Thailand (Pfeiffer 1856a) and then from Laos (Saurin 1953;Inkhavilay et al. 2019). However, the specimens from Laos are shells only, and so the distribution of S. hainesi s. s. in Laos still needs to be confirmed. Diagnosis. Shell large, depressed, obtusely angulated body whorl and higher shell spire. Animal with pale to dark grey body and four mantle lobes. Genitalia with a large and straight epiphallic caecum, and triangular prism shaped penial pilasters. Spermatophore with irregularly acute-serrate longitudinal ridges on the head filament, tail filament with two spines and more than ca. two-thirds of its length with series of short branching spines.

Sarika bocourti
Description. Shell. Shell depressed, large to very large size (shell width up to 33.1 mm, shell height up to 16.1 mm) and rather thin. Shell surface smooth and polished; shell colour pale yellowish brown to brown. Whorls 6-7, increasing regularly; body whorl large and obtusely angulated. Spire moderately to very much elevated; suture impressed. Aperture crescent-shaped and obliquely opened. Peristome simple. Columellar margin simple and slightly reflected near umbilicus. Umbilicus narrowly opened (Fig. 34D-F).
Genital organs. Atrium short. Penis cylindrical with thin penial sheath covering proximal penis. Inner sculpture of penis proximally more than ca. half of penial chamber with very finely longitudinal penial pilasters to nearly smooth surface, and then gradually transformed from small to large rhomboid pilasters with acute angle on top (triangular prism). Epiphallus cylindrical, slightly longer than penis, and approximately same diameter as penis. Epiphallic caecum short, straight, approximately similar diameter with penis, and located near middle of epiphallus. Penial retractor muscle thin and attached at tip of epiphallic caecum. Flagellum long slender and slightly longer than epiphallus. Vas deferens thin tube connecting distal epiphallus and free oviduct (Fig. 35C, D).
Vagina cylindrical and approximately as long as penis. Dart apparatus enlarged, long cylindrical, and located on atrium at vagina and penis junction. Gametolytic sac enlarged and bulbous (with spermatophore inside); gametolytic duct cylindrical. Free oviduct cylindrical, nearly two times of vagina length, and proximal end encircled with thick tissue (Fig. 35C).
Spermatophore long and needle-shaped. Sperm sac enlarged and elongate-oval. Head filament gourd shape with irregularly acute-serrate longitudinal ridges. Tail filament very long tube; region near sperm sac with two spines. Spine I simple and rather short. Spine II very large at base and divided in two spines and then each one branching into many spinules near the tip. Region furthest away smooth without spine; terminal part (more than ca. two-thirds of its length) with series of short branching spines arranged in a row and transformed to long serrate-like spines arranged in opposite rows near the tail filament tip (Fig. 37).
Radula. Teeth with half row formula: 1-(12-13)-61. Central tooth symmetrical tricuspid with large mesocone and very small to nearly absent ectocone; lateral teeth asymmetrical tricuspid with large mesocone and very small to nearly absent endocone and ectocone; marginal teeth elongate bicuspid. Marginal teeth starting at approximately row number 12 or 13 (Fig. 43B).
External features. Animal with reticulated skin, pale to dark grey body and darker than foot sole, and dark grey caudal horn. Mantle edge well developed and pale grey colour. Shell lobes and dorsal lobes shape and structure like S. hainesi (Fig. 33A, C).
Distribution. This species is known from several localities in Chanthaburi Province, eastern Thailand and Surat Thani, Nakhon Si Thammarat and Phang-nga provinces, southern Thailand (Fig. 32), and Battambang Province, Cambodia (Morelet 1875; Pholyotha et al. 2020a). Sarika bocourti is common in both human-influenced habitats, such as plantations or gardens, and natural habitats. COI analysis. The ML and BI analyses showed that the four specimens of S. bocourti represent a single haplotype, sister group to S. inferospira sp. nov. + S. melanospira sp. nov. with strong support (Fig. 1; BS = 99%, PP = 1). Remarks. Specimens from Chanthaburi Province, eastern Thailand were identical with the syntype of S. bocourti that was described from Battambang Province, Cambodia. Both the shell morphology and genital anatomy of the disjunct populations from southern Thailand agree well with the populations from eastern Thailand. From the COI gene phylogeny, all specimens from southern Thailand are retrieved as monophyletic with S. bocourti from eastern Thailand and with no variation in the COI sequences ( Table 2). The eastern and southern populations of S. bocourti are possibly shaping up by sea level fluctuation in the last glacial periods recorded in tree-dwelling snails and centipedes (Prasankok et al. 2007;Siriwut et al. 2015). Further investigation by adding more samples and genetic markers would help elucidate the phylogeographical history of this species.
Although shell morphology of S. bocourti and S. hainesi is quite similar, the genitalia and spermatophore are clearly distinct. Sarika bocourti has larger epiphallic caecum, and a spermatophore with a head filament with acute-serrate ridges, and the tail filament has fewer branching spines. Sarika hainesi has a smaller epiphallic caecum, and a spermatophore with a head filament with a sponge-like appearance and the tail filament has more branching spines. In addition, the genetic distance between these two species is rather high (7.0%). Type locality. Wat Tham Sai Thong, Nong Kung Si, Kalasin, Thailand, 16°50'11.3"N, 103°14'18.7"E.

Sarika inferospira
Diagnosis. Shell large, strongly depressed, very pale yellowish brown with shouldered body whorl. Animal with grey colour and four mantle lobes. Genitalia with a large straight epiphallic caecum, and triangular prism pilasters on inner penial sculpture. Spermatophore: tail filament near sperm sac with two spines and a series of several branching spines occurring continually to the middle region; middle region becoming smooth, spineless and then terminal part approximately half of its length with a series of branching spines.
Description. Shell. Shell strongly depressed, large size (shell width up to 29.3 mm, shell height up to 13.9 mm) and thin. Surface smooth and polished; shell colour very pale yellowish brown. Whorls 6-6½, increasing regularly; body whorl large and shouldered. Spire slightly elevated; suture impressed. Aperture crescent-shaped and obliquely opened. Peristome simple. Columellar margin simple and slightly reflected near umbilicus. Umbilicus narrowly opened (Fig. 38A, B).
Genital organs. Atrium short. Penis cylindrical with thin penial sheath covering proximal penis. Inner sculpture of penis proximally more than ca. half of penial chamber with very finely longitudinal penial pilasters to nearly smooth surface, and then gradually transformed from small to large rhomboid pilasters with acute angle on top (triangular prism). Epiphallus cylindrical and approximately the as long as penis. Epiphallic caecum short, straight, diameter larger than epiphallus, and located near middle of epiphallus. Penial retractor muscle thin and attached at tip of epiphallic caecum. Flagellum long, slender and nearly one and half times of epiphallus length. Vas deferens thin tube connecting distal epiphallus and free oviduct (Fig. 39A, B).
Vagina cylindrical, short, and approximately two-third of penis length. Dart apparatus large, long cylindrical and located on atrium at vagina and penis junction. Gametolytic sac enlarged and bulbous; gametolytic duct long cylindrical. Free oviduct cylindrical, approximately two and half times of vagina length (Fig. 39A).
Spermatophore long and needle-shaped. Sperm sac enlarged and elongate-oval. Head filament was missing (incomplete spermatophore). Tail filament very long tube and region near sperm sac with two spines. Spine I simple and long. Spine II slightly longer and larger than spine I and branching into many small spinules. Continuously on tail filament with short branching spines arranged in a row, modified to longer branching spines arranged in several rows around middle region, and then become smooth and without spine (Fig. 40A at yellow line). Terminal part of tail filament (more than ca. one-fourth of its length) with series of long branching spines arranged in opposite rows and tail filament tip with no spine (Fig. 40).
External features. Animal with reticulated skin and body colour with dark grey above and creamy-grey below. Creamy-grey foot sole and dark creamy-grey caudal horn. Four mantle lobes well developed and pale grey colour. Left shell lobe absent (Fig. 33D).
Etymology. The specific epithet inferospira is derived from the Latin word infer meaning low and the Latin word spira meaning coil. It refers to the strongly depressed shell with low spire.
Distribution. Sarika inferospira sp. nov. is only known from sandstone habitats with dry dipterocarp forest at the type locality (Fig. 32).
Remarks. Sarika inferospira sp. nov. is distinguished from S. hainesi and S. bocourti by having a strongly depressed shape, shouldered body whorl, and spermatophore smooth or without spine on the middle part of tail filament. Sarika hainesi and S. bocourti have a depressed shell with a higher spire and obtusely angulated body whorl. In addition, the tail filament of spermatophore contains a series of short branching spines more than ca. half of its length in S. hainesi and more than ca. two-thirds of its length in S. bocourti. Type locality. Wat Tham Suwan Phu Pha,Khao Chamao,Rayong,Thailand,12°59'24.1"N,101°39'28.8"E. Diagnosis. Shell large, dextral, depressed and pale brown with rounded to weak shouldered body whorl. Animal with blackish body, four mantle lobes and mantle covered by spiral black band below the suture at the body whorl. Genitalia with a large straight epiphallic caecum and triangular prism pilasters on inner penial sculpture.

Sarika melanospira
Description. Shell. Shell depressed, large size (shell width up to 29.3 mm, shell height up to 13.3 mm) and thin. Surface smooth and polished; shell colour pale brown.
Genital organs. Atrium short. Penis cylindrical with thin penial sheath covering proximal penis. Inner sculpture of penis proximally more than ca. half of penial chamber with very finely longitudinal penial pilasters to nearly smooth surface, and then gradually transformed from small to large rhomboid pilasters with acute angle on top (triangular prism). Epiphallus cylindrical and nearly two times penis length. Epiphallic caecum short, straight, slightly larger than epiphallus and located near middle of epiphallus. Penial retractor muscle thin and attached at tip of epiphallic caecum. Flagellum slender, narrower than epiphallus and approximately as long as penis. Vas deferens thin tube connecting distal epiphallus and free oviduct (Fig. 39C, D).
Vagina long cylindrical and approximately as long as penis. Dart apparatus large, long cylindrical, and located on atrium at vagina and penis junction. Gametolytic sac enlarged and bulbous; gametolytic duct long cylindrical. Free oviduct cylindrical, nearly as long as vagina (Fig. 39C).
External features. Animal with reticulated skin and blackish body. Mantle with conspicuous blackish spiral band at the body whorl below the suture. Creamy-grey foot sole and blackish caudal horn. Four mantle lobes well developed and blackish. Left shell lobe absent (Fig. 33E).
Etymology. The specific epithet melanospira is derived from the Greek word melanos meaning black or dark, and the Latin word spira meaning coil. It refers to the mantle being covered by a spiral black band at the body whorl.
Distribution. Sarika melanospira sp. nov. is only known from the limestone habitats at the type locality (Fig. 32).
Remarks. Among the Sarika hainesi group, this new species differs from S. hainesi, S. bocourti, and S. inferospira sp. nov. in having a rounded to very weak shouldered body whorl. Sarika hainesi and S. bocourti have an obtusely angulated body whorl and S. inferospira sp. nov. has a shouldered body whorl.
Diagnosis. Shell large, depressed to strongly depressed, pale brown to dark brown with rounded to weak shouldered body whorl. Animal with blackish body and four mantle lobes. Genitalia with a large straight epiphallic caecum and triangular prism pilasters on inner penial sculpture. Spermatophore: tail filament near sperm sac with three spines and terminal part more than ca. one-third of its length with series of branching spines.
Description. Shell. Shell depressed to strongly depressed, large size (shell width up to 24.7 mm, shell height up to 12.0 mm), and thin. Surface smooth and shiny; shell colour very pale brown to dark brown. Whorls 6-6½, increasing regularly; body whorl large and rounded to weak shouldered. Spire moderately elevated; suture impressed. Aperture crescent-shaped and obliquely opened. Peristome simple. Columellar margin simple and slightly reflected near umbilicus. Umbilicus narrowly opened (Fig. 38E, F).
Genital organs. Atrium short. Penis cylindrical with thin penial sheath covering proximal penis. Inner sculpture of penis proximally more than ca. half of penial chamber with very finely longitudinal penial pilasters to nearly smooth surface, and then gradually transformed from small to large rhomboid pilasters with acute angle on top (triangular prism). Epiphallus enlarged cylindrical and approximately two times penis length. Epiphallic caecum large, straight, similar to epiphallus diameter and located near middle of epiphallus. Penial retractor muscle thin and attached at tip of epiphallic caecum. Flagellum long and enlarged approximately as long as epiphallus. Vas deferens thin tube connecting distal epiphallus and free oviduct (Fig. 41). Vagina long cylindrical and approximately twice as long as penis. Dart apparatus large, long cylindrical, and located on atrium at vagina and penis junction. Gametolytic sac enlarged and bulbous; gametolytic duct enlarged cylindrical (spermatophore inside). Free oviduct cylindrical, slightly shorter than vagina (Fig. 41A).
Spermatophore long and needle-shaped. Sperm sac enlarged and elongate-oval. Head filament was missing (incomplete spermatophore). Tail filament very long tube; region near sperm sac with three spines. Spine I simple and rather short. Spine II large and long, and most of branching spines probably missing. Spine III smaller than spine II, branching into small spines and spinules. Region furthest away smooth and without spine; terminal part (more than ca. one-third of its length) with series of long branching spines arranged in a row or encircled the tail filament tip (Fig. 42).
Etymology. The specific name pellosa is from the Greek word pellos meaning dusky and refers to the blackish body that characterises this species.
Distribution. This species is only known from several limestone karsts in Sa Kaeo Province (Fig. 32).
Remarks. The shell of S. pellosa sp. nov. differs from other species in Sarika hainesi group by having a rounded to very weak shouldered body whorl. In contrast, the shells of S. hainesi and S. bocourti have obtusely angulated body whorls and S. inferospira sp. nov. has a shouldered body whorl.
The shell of this new species is generally similar to S. melanospira sp. nov. The distinguishing characters of S. pellosa sp. nov. are a broader body whorl, larger size of flagellum, vagina and free oviduct, and animal without a dark spiral band, while S. melanospira sp. nov. has a broad body whorl, smaller size of flagellum, vagina and free oviduct, and animal with a dark spiral band below the suture at the body whorl. In addition, the average interspecific sequence divergences between S. pellosa sp. nov. and S. melanospira sp. nov. are fairly high (6.6%). Therefore, we treat them as two separate species. Fischer 1891: 20. Nanina (Macrochlamys) dugasti: Fischer and Dautzenberg 1904: 395. Sarika dugasti: Tomlin 1929: 16. Maneevong 2000Sutcharit and Panha 2008: 96;Schileyko 2011: 34. Inkhavilay et al. 2019Pholyotha et al. 2020c: 19, Fig. 9f.  shell colour very pale to dark brown. Whorls 6½-7½, increasing regularly; body whorl large and well rounded. Spire much elevated; suture impressed. Aperture crescent-shaped and obliquely opened. Peristome simple and slightly thickened. Columellar margin simple and slightly reflected near umbilicus. Umbilicus narrowly opened (Fig. 46A, B).
Genital organs. Atrium short. Penis long cylindrical with thin penial sheath covering penis. Proximal penis rather slender; distal penis enlarged with pseudo-verge inside. Inner sculpture of penis proximally with very finely longitudinal penial pilasters to nearly smooth surface, then transformed to small cuboidal and reticulated pilaster in middle and modified to larger cuboidal pilasters at distal end. Pseudo-verge elon- gate conic and approximately one-third of penis length. Epiphallus cylindrical, and narrower than distal penis. Epiphallic caecum very long, straight, and same diameter as epiphallus. Penial retractor muscle thin and attached at tip of epiphallic caecum. Flagellum long, slender, and approximately as long as penis. Vas deferens thin tube connecting distal epiphallus and free oviduct (Fig. 47A, B).
Vagina short and approximately one-third of penis length. Dart apparatus large, long cylindrical, and located on atrium at vagina and penis junction. Gametolytic organ (sac and duct) small and long cylindrical tube. Free oviduct cylindrical, approximately as long as vagina, and proximal end encircled with thick tissue (Fig. 47A).
External features. Animal with reticulated skin, greyish body, slightly pale colour on foot sole and darker colour on caudal horn. Mantle edge well developed with three dorsal lobes and two shell lobes, and similar colour to body (Fig. 45A).
Distribution. Sarika dugasti occurs in central, north and western Thailand along the Tenasserim Ranges (Fig. 44) and the Salween Valley, east of the Dawna Ranges in Myanmar (Blanford and Godwin-Austen 1908;Pholyotha et al. 2020c). However, the literature records from Laos, Nepal and Vietnam (Schileyko 2011;Inkahvilay et al. 2019) are still uncertain.
COI analysis. The ML and BI analyses revealed that the individuals of S. dugasti (n = 3) formed a monophyletic group with good support ( Fig. 1; BS = 91%, PP = 1). The mean intraspecific genetic distance of S. dugasti was 3.7% (Table 2).
Remarks. Sarika dugasti can be distinguished from all other known Sarika species by having a dome-shaped shell with narrow aperture and genitalia with a very long epiphallic caecum and long pseudo-verge. Other Sarika species tend to have a flattened to depressed shell with a wide aperture and genitalia without penial verge. Although we surveyed during the wet season, only immature snails were collected, and so the radula and genitalia of sub-adult specimens are illustrated here.  Type locality. The limestone karsts with dry forest near Mae La Na Cave, Pang Mapha, Mae Hong Son, Thailand, 19°34'25.5"N, 98°13'01.8"E.

Sarika solemi
Diagnosis. Shell large, depressed and yellowish brown to brown with obtusely angulated to angulated body whorl. Animal with creamy-grey body and five mantle lobes. Genitalia with a long straight epiphallic caecum and long pseudo-verge. Inner penial sculpture with irregularly short folded pilasters in proximal part, then reticulated pilasters in the middle, and cuboidal pilasters in distal end.
Description. Shell. Shell depressed, large size (shell width up to 26.5 mm, shell height up to 15.0 mm) and rather thin. Surface rather smooth and polished; shell colour yellowish brown to brown. Whorls 6-6½, increasing regularly; body whorl large and obtusely angulated to angulated. Spire moderately to very much elevated; suture impressed. Aperture crescent-shaped and obliquely opened. Peristome simple. Columellar margin simple and slightly reflected near umbilicus. Umbilicus narrowly opened ( Fig. 46C-F).
Genital organs. Atrium short. Penis cylindrical with thin penial sheath covering proximal penis. Proximal penis rather slender; distal penis enlarged with pseudoverge inside. Inner sculpture of penis proximally with very finely longitudinal penial pilasters to nearly smooth surface, then changed to irregularly short folded pilasters, modified to reticulated pilasters in middle, and modified to cuboidal pilasters at distal end. Pseudo-verge long conic, approximately one-third of total penis length. Epiphallus long cylindrical and narrower than distal penis. Epiphallic caecum very long, straight, and almost same diameter as epiphallus. Penial retractor muscle thin and attached at tip of epiphallic caecum. Flagellum long slender, and approximately as long as penis. Vas deferens thin tube connecting distal epiphallus, and free oviduct (Fig. 47C, D).
Vagina cylindrical and approximately one-fourth of penis length. Dart apparatus large, long cylindrical, and located on atrium at vagina and penis junction. Gametolytic organ (sac and duct) small and long duct. Free oviduct cylindrical and proximal end encircled with thick tissue (Fig. 47C).
External features. Animal with reticulated skin and dark creamy mixing with grey to dark grey body, very pale grey foot sole and pale grey caudal horn. Five mantle lobes well developed and same colour as body (Fig. 45B).
Etymology. The specific name solemi is named in honor of Dr. Alan Solem, who first discovered and described the genitalia of this species but under the name Sarika aff. hainesii.
Distribution. Sarika solemi sp. nov. seems to be restricted to western and northern Thailand along the Tenasserim Ranges (Fig. 44). This species occurs in forested mountains and is highly abundant in limestone habitats. COI analysis. The ML and BI analyses showed that the individuals of S. solemi sp. nov. (n = 3) formed a monophyletic group with high support ( Fig. 1; BS = 95%, PP = 1). The mean intraspecific genetic distance of S. solemi sp. nov. was 2.9% (Table 2).
Remarks. Solem (1966) examined and described the genitalia of specimens from northern Thailand and referred them to as "Sarika aff. hainesii". In this study, we collected and examined several new specimens from northern Thailand and found that the genitalia were identical with those described and illustrated in Solem (1966: 38, 39 , fig 5a). We here recognised these populations as new species. Sarika solemi sp. nov. has similar shell morphology to S. hainesi s.s., but the distinguishing characters are the number of mantle lobes and genitalia. This new species has five mantle lobes and genitalia with very long epiphallic caecum and long pseudo-verge, while S. hainesi s. s. has four mantle lobes, and genitalia with shorter epiphallic caecum and without pseudo-verge.
Sarika solemi sp. nov. is a variable species in terms of body whorl with obtusely angulated periphery (Fig. 46C, D) to obvious angulated periphery (Fig. 46E, F). All shell morphs are identical in genital characters and form a well-supported clade in COI analysis.

Species of doubtful status or uncertain record for Thailand
The following six species have never been examined for their genitalia and no living specimens could be collected in this study. However, we assign them to the genus Sarika following current literature and based on their shell characters. They have a relatively large shell diameter (greater than 20 mm), and a smooth and polished shell surface. Macrochlamys from Thailand (Pholyotha et al. 2018) tend to have a much smaller shell diameter (less than 20 mm) than the genus Sarika (see Table 5). However, living specimens are still necessary for examination of the reproductive organs to ascertain their generic placement. Other material examined. Thailand-Northeastern. Dry dipterocarp forest at Phu Lan Kha, Nong Bua Daeng, Chaiyaphum, 16°00'00.9"N, 101°52'33.4"E: CUMZ 7277.
Diagnosis. Shell medium-sized, depressed to strongly depressed, and pale brown. Aperture irregular with peristome rather simple above then expanded middle with curved inside aperture and thickened below periphery.
Description. Shell. Shell depressed to strongly depressed or nearly flattened, medium-sized (shell width up to 17.4 mm, shell height up to 8.8 mm), rather thin, and slightly opaque. Shell surface smooth, polished and with thin growth lines; shell colour pale brown. Whorls 6-7, increasing regularly; body whorl large and well rounded. Spire little to moderately elevated; suture impressed. Aperture crescent-shaped and open obliquely; peristome irregular. Apertural lip at upper periphery simple; at periphery with invagination of triangular lip (beak-like); at below periphery rather thickened inside aperture and little expanded. Columellar margin straight, slightly thickened and expanded near umbilicus. Umbilicus narrowly opened (Fig. 50A, B). Etymology. The specific name gratesi is named in honour to Admiral Chorchat Gra-tes of the Royal Thai Navy, who made possible many fieldtrips especially the remote islands areas in Thailand.
Distribution. Sarika gratesi sp. nov. is currently known from the restricted area of the dry deciduous and dry dipterocarp forests in Khon Kaen and Chaiyaphum provinces (Fig. 49).
Remarks. This new species is easy to distinguish from all known Sarika as well as Macrochlamys species by its unique beak-like lip, while all other species in these two genera have simple to little thickened lips. Only, Macrochlamys aspides (Benson, 1863) from Myanmar tends to have a slightly thickened and expanded lip at below periphery, but Sarika gratesi sp. nov. has a projecting and curved triangular shape lip at the periphery. Sarika gratesi sp. nov. is identical to Sarika because its shells are matched with Sarika more than the Siam Macrochlamys (Pholyotha et al. 2018). ( Type material. The type specimen could not be located in the NHM collections.

Sarika subcornea
Diagnosis. Shell depressed, medium size (shell width up to 13.6 mm, shell height up to 6.0 mm) and thin. Shell surface smooth and shining; shell colour whitish horny. Whorls 7½, increasing regularly; body whorl well rounded. Spire elevated; suture impressed. Aperture crescent-shaped and obliquely opened. Peristome simple and slightly thickened. Columellar margin simple. Umbilicus narrowly opened.
Remarks. The original description is not illustrated, type specimen could not be traced, and no new specimens have been reported so far. Hanley and Theobald (1876: 59, pl. 149, Figs 2, 3) illustrated this species based on a specimen from "Phie Than" [Payathonzu, Myanmar]. But, Blanford and Godwin-Austen (1908) stated that this specimen was instead a juvenile shell of S. resplendens. Recently, Maassen (2001) also reported S. subcornea as a new record from Kedah, Malaysia, but unfortunately without illustration. Therefore, the taxonomic status of this species is still unclear, and we retained this species within the genus Sarika as per Maassen (2001). Godwin-Austen (1883) noted that S. subcornea is distinguished from other species by the relatively more numerous and more closely wound whorls. Macrochlamys benoiti : Ancey 1898: 128, pl. 9, Fig. b;Saurin 1953: 113;Schileyko 2011: 30, 31. Sarika benoiti: Inkhavilay et al. 2019: 81, Fig. 38c;Pholyotha et al. 2020a: 7. Type material. No type material could be located in the MNHN collections. The illustration from the original description is reproduced here (Fig. 50F).
Remarks. This species was described based on a specimen from south-central Vietnam (Crosse and Fischer 1863). Up to now, Sarika benoiti has been recorded throughout the Indochina countries (Ancey 1898, Fischer and Dautzenberg 1904, Saurin 1953, Schileyko 2011, Inkhavilay et al. 2019). However, these records remain equivocal and tentative because of unavailable distinguished genital data. In Thailand, Sarika benoiti was recorded from eastern Thailand based on specimens from the Pavie collection (Fischer and Dautzenberg 1904).
In this study, the specimens from the eastern part of Thailand agreed well with the syntype of S. bocourti (Fig. 34A) where its type locality is in Battambang, Cambodia. Based on shell morphology, S. benoiti (Fig. 50F) differs slightly from S. bocourti in having a smaller sized and well-rounded body whorl, whereas S. bocourti has a larger sized shell (shell width up to 33 mm) and obtusely angulated body whorl. Other material examined. Siam: NHMUK 1901.1.6.246 (one broken shell, specimen dissected by Godwin-Austen 1907) ex. Daly collection.
Diagnosis. Shell depressed to conoid-depressed, large size (shell width up to 26.0 mm, shell height up to 16.0 mm) and rather thin. Shell surface smooth, slightly shining above and more shining below; shell colour brownish. Whorls 7, increasing regularly; body whorl large and obtusely angulated. Spire high-conical; suture impressed.
Remarks. Godwin-Austen (1907: 181, pl. 116, Fig. 1) examined the rehydrated specimens from Thailand and placed this species in the genus Sarika. We have examined the specimen dissected (only shell remained) by Godwin-Austen (NHMUK 1901.1.6.246) and noticed that the shell morphology slightly differs from the syntypes. The dissected specimen has a rounded body whorl and lower spire, whereas the syntypes have obtusely angulated body whorl and higher spire. Unfortunately, we could not find any specimens identical to the syntypes during this survey. Additional specimens with precise collection locality and anatomical studies are necessary to confirm the taxonomic position of this species.
Remarks. Compared to the species with shell width greater than 30 mm, S. ochtogyra can be distinguished from S. rex by having eight whorls and obtusely angulated periphery, while S. rex has seven whorls and rounded periphery.
Sarika ochtogyra is currently known only from the type locality in Thailand. Originally, it was described based on a collection made by the butterfly collector, H. Frühstorfer (Lamas 2005). The type locality "Siam: Bangkok" is probably not the location where the type specimen was collected. After surveys throughout Thailand, we could find neither Sarika nor Macrochlamys with large shell sizes that match well with the type specimen.
Type material. The unique name bearing type could not be located. The photograph of the type specimen from the original description is reproduced herein (Fig. 50G).
Diagnosis. Shell conoid-depressed, large to very large size (shell width up to 30.0 mm, shell height up to 16.0 mm) and thin. Shell surface rather smooth with fine growth lines, polished below but not polished above; shell colour pale yellowish brown. Whorls 6½, increasing regularly; body whorl large and rounded. Spire very high-conical; suture impressed. Aperture crescent-shaped and obliquely opened. Peristome simple. Columellar margin simple. Umbilicus narrowly opened (Fig. 50G).
Remarks. We assigned this species to the genus Sarika due to its very large shell size, and none of any Macrochlamys species could reach that diameter (Table 5). Preston (1909) noted that S. rex is a large-sized species and is generally similar to S. pumicata, but S. rex tended to have more tumid and higher spire than S. pumicata, as well as a rounded body whorl, whereas S. pumicata has an obtusely angulated periphery.
Sarika rex is known only from the type locality in Thailand; however, the precise type locality could not be determined. To date, no living specimen that matches this species has been found, and the generic assignment is still provisional. New specimens with precise collection locality and genital anatomy are necessary to verify the taxonomic position of this species.

Conclusions
This study updates the state of knowledge of malacofaunal diversity in Thailand and the results increase the number of Sarika species recognised in the country to 23, nine of which are new species. Our analyses of morphology and molecular phylogeny resolve and support all Sarika species anatomically examined herein (see Fig. 1; Tables 2-5).
Sarika resplendens is regarded as one of the most common and widespread snail species in Thailand and this species is believed to have been accidentally introduced by human activities. However, most of the Sarika species have narrow distributional ranges restricted to individual habitats such as sandstone, granite, limestone or forested mountainous areas, and they show allopatric and sympatric distribution patterns, possibly resulting from limited dispersal abilities and the complex geography of the areas. The low dispersal capacities and a narrow ecological niche of land snails may reduce genetic exchange between populations (Shimizu and Ueshima 2000). A conspicuous feature of Thailand is the many extensive ranges of limestone karsts and outcrops scattered throughout the country (Gupta 2005;Naggs et al. 2006;Ridd et al. 2011). Limestone karsts in the humid tropics contain a high diversity of microhabitats that are conducive for land snail speciation and endemism (Clements et al. 2006;Foon et al. 2017).
The subdivision of Sarika into three groups (resplendens, hainesi, and dugasti) has been not yet resolved. Therefore, future studies combined with other genetic markers for molecular phylogenetic analyses will be necessary to clarify these subdivisions and may reveal a hypothesis of the evolution and biogeography of this genus. Table 3. Shell measurements of Sarika species in Thailand. The superscript indicates spermatophore morphology reference: 1 this study, 2 Pfeiffer (1861), 3 Crosse and Fischer (1863), 4 Morelet (1875), 5 Möllendorff (1902), and 6 Preston (1909).