Research Article |
Corresponding author: Piyoros Tongkerd ( piyorose@hotmail.com ) Academic editor: Frank Köhler
© 2021 Parin Jirapatrasilp, Barna Páll-Gergely, Chirasak Sutcharit, Piyoros Tongkerd.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Jirapatrasilp P, Páll-Gergely B, Sutcharit C, Tongkerd P (2021) The operculate micro land snail genus Dicharax Kobelt & Möllendorff, 1900 (Caenogastropoda, Alycaeidae) in Thailand, with description of new species. Zoosystematics and Evolution 97(1): 1-20. https://doi.org/10.3897/zse.97.59143
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This study reviews the Dicharax species in Thailand. Altogether ten Dicharax species are reported, four of which are new to science and described herein. They are Dicharax borealis Jirapatrasilp & Páll-Gergely sp. nov., Dicharax burchi Jirapatrasilp & Páll-Gergely sp. nov., Dicharax panhai Jirapatrasilp & Páll-Gergely sp. nov. and Dicharax pongrati Jirapatrasilp & Tongkerd sp. nov. Alycaeus davisi Godwin-Austen, 1914 is regarded as a junior subjective synonym of Alycaeus cucullatus Theobald, 1870 (= D. cucullatus) based on a similar depressed-conical shell shape, a long sutural tube and a sharp swelling behind the peristome. Furthermore, the type locality of Alycaeus pratatensis Panha & Burch, 1997 (= D. pratatensis) had to be amended. Most important characters to distinguish Dicharax species are the general shell shape and relative lengths of teleoconch regions, whereas the spiral striation of R1, the shape of swelling of R3, the outer peristome crenulation and protrusion, and the exterior opercular sculpture show large intraspecific variability.
Cyclophoroidea, Gastropoda, Mollusca, taxonomy
Alycaeidae Blanford, 1864 is a family of cyclophoroidean operculate land snails. The alycaeid shell is characterized by a sutural tube that corresponds with numerous perpendicular microtunnels as described by
List of species in the family Alycaeidae reported from Thailand. Some species recorded in
Species [Original genus] | Type locality | Distribution records | References |
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Alycaeus conformis Fulton, 1902 | Perak State, Malaysia | Malaysia: Kelantan, Pahang, Selangor and Johor |
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Thailand: Bangpae waterfall, Phuket | |||
Alycaeus gibbosulus Stoliczka, 1872 | Penang Island, Malaysia | Peninsular Malaysia Thailand: Khao Chong, Trang |
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Alycaeus somwangi Dumrongrojwattana & Maassen, 2008 | Lub Lae Cave, Chonburi Province, Eastern Thailand | Only the type locality |
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Chamalycaeus canaliculatus (Möllendorff, 1894) [Alycaeus] | Samui Islands, Gulf of Siam | Only the type locality |
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Dicharax caudapiscis Páll-Gergely & Hunyadi, 2018 | Wat Tham Pla, approx. 9 km south-southwest from Mae Sai, Chiang Rai Province, Northern Thailand | Only the type locality |
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Dicharax cucullatus (Theobald, 1870) (syn. nov. Alycaeus davisi Godwin-Austen, 1914) [Alycaeus] | Shan States | Myanmar: Shan State |
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Thailand: Doi Chiang Dao, Doi Ang Khang and Doi Inthanon, Chiang Mai | |||
Dicharax notus (Godwin-Austen, 1914) [Alycaeus] | Fort Stedman, Burma | Myanmar: Shan State |
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Thailand: Tham Luang Sa Koen, Nan | |||
Dicharax omissus (Godwin-Austen, 1914) [Alycaeus] | Siam and Shan boundary | Myanmar: Shan State |
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Thailand: Tham Mae Lana, Mae Hong Son | |||
Dicharax pratatensis (Panha & Burch, 1997) [Alycaeus] | Doi Chiang Dao, Chiang Mai Province, Northern Thailand [non Pratat cave, Erawan National Park, Kanchanaburi Province] | Only the type locality |
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Dicharax stuparum Páll-Gergely & Hunyadi, 2018 | 50 m before Wat Phra That Doi Tung, around the car park, Doi Tung, Chiang Rai Province, Northern Thailand | Only the type locality |
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Dicharax borealis Jirapatrasilp & Páll-Gergely sp. nov. | Tham Ban Luang, Doi Ang Khang, Chiang Mai Province, Northern Thailand | Only the type locality | This study |
Dicharax burchi Jirapatrasilp & Páll-Gergely sp. nov. | Tham Phaya Nakharat, Khon Kaen Province, Northeastern Thailand | Myanmar: Hsihseng centre, Shan State | This study |
Thailand: Doi Chiang Dao, Chiang Mai and Ban Soppong, Mae Hong Son | |||
Dicharax panhai Jirapatrasilp & Páll-Gergely sp. nov. | Pratat cave, Erawan National Park, Kanchanaburi Province, Western Thailand | Only the type locality |
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Dicharax pongrati Jirapatrasilp & Tongkerd sp. nov. | Doi Chiang Dao, Chiang Mai Province, Northern Thailand | Only the type locality | This study |
Dioryx distortus (Haines, 1855) [Cyclostoma] | Siam | Thailand |
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Stomacosmethis christae (Maassen, 2006) [Alycaeus] | at km 117.6 of road # 4 (Krabi – Phang Nga), Krabi Province, Southern Thailand | Only the type locality |
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Stomacosmethis matchacheepiorum (Dumrongrojwattana & Maassen, 2008) [Alycaeus] | Khao Pratun Cave, Rayong Province, Eastern Thailand | Only the type locality |
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Stomacosmethis perakensis (Crosse, 1879) [Alycaeus] | Buket Pondong, Perak | Malaysia: Kedah and Perak |
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Thailand: Banang Pupo, Yala | |||
Stomacosmethis roebeleni (Möllendorff, 1894) [Alycaeus] | Samui Islands, Gulf of Siam | Malaysia: Perlis |
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Thailand: Patthalung | |||
Stomacosmethis somnueki (Panha & Patamakanthin, 2001) (syn. A. huberi Thach, 2018) [Alycaeus] | Ao Luk limestone areas, Krabi Province, Southern Thailand | Only the type locality |
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Dicharax Kobelt & Möllendorff, 1900 (replacement name for Charax Benson, 1859, non Charax Scopoli, 1777 [Pisces]) is one of the seven genera of the Alycaeidae (
In the present paper, based on the examination of the
This study is based on material collected from throughout Thailand since 1996 which is now deposited in the collection of the Chulalongkorn University (
Geographical position of the type localities (white number in black circle) and other examined localities (black number in white circle) of Dicharax spp. in this study. No. 1: D. cucullatus, 2: D. notus, 3: D. omissus, 4: D. pratatensis, 5: D. borealis sp. nov., 6: D. burchi sp. nov., 7: D. panhai sp. nov., 8: D. pongrati sp. nov. The type localities of D. cucullatus and D. omissus (Shan States and Siam and Shan boundary, respectively) are general and not plotted in the figure.
SH, shell height; SW, shell width.
“Doi”, Mount; “Tham”, Cave; “Wat”, Temple.
Family Alycaeidae Blanford, 1864
Alycaeus (Charax)
Benson, 1859: 177;
Alycaeus (Dicharax)
Kobelt & Möllendorff, 1900: 186 (replacement name for Charax Benson, 1859, non Charax Scopoli, 1777 [Pisces]);
Chamalycaeus (Dicharax)
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Chamalycaeus (Sigmacharax)
Kuroda, 1943: 8;
Chamalycaeus (Cipangocharax)
Kuroda, 1943: 11;
Chamalycaeus (Awalycaeus)
Kuroda, 1951: 73, 74;
Dicharax
–
Alycaeus hebes Benson, 1857, by subsequent designation (
Alycaeus cucullatus
Theobald, 1870: 396, 397, pl. 18, fig. 2. Type locality: Shan States [Myanmar].
Alycaeus (Charax) cucullatus
–
Alycaeus davisi Godwin-Austen, 1914: 408, pl. 148, fig. 9, 9a. Type locality: Siam and Shan State boundary. New synonym.
Alycaeus (Dicharax) cucullatus
–
Alycaeus (Chamalycaeus) davisi
–
Dicharax cucullatus
–
Dicharax davisi
–
Syntypes
of Alycaeus cucullatus NHMUK 1888.12.4.951–952 from Shan States (2 shells; Fig.
Dicharax cucullatus from Chiang Mai Province A. Specimen
Shell medium-sized (SH up to 3.5 mm, SW up to 5.5 mm), depressed-conical. Spire ca. 1/5 of shell height. R1 with regular, strong ribs; R2 longer than R3; R2 with 49–57 ribs. R3 with sharp swelling near aperture. Aperture round. Inner peristome with four to five indentations, always with parieto-columellar indentation, sometimes weak at basal. Outer peristome fringed, slightly reflected but not conspicuous. Umbilicus round. Operculum multispiral with elevated lamella.
Shan State, Myanmar (
This species was originally described from Shan State and diagnosed by its fringed peristome with five indentations (
A, B. Dicharax cucullatus, specimens
Dicharax cucullatus differs from other species with similar shell shape and fringed peristome, i.e. D. anthostoma (Möllendorff, 1885) (
Some specimens from Doi Inthanon possess a more depressed shell with a lower spire, a very low swelling of R3 and a nearly smooth inner peristome (Fig.
Alycaeus notus Godwin-Austen, 1914: 411, pl. 155, fig. 12. Type locality: Fort Stedman, Burma [Maing Thauk or Mine Thauk located in the east side of Inle Lake south of Nyaungshwe, Nyaungshwe Township, Taunggyi District, Shan State, Myanmar].
Alycaeus (Dicharax) notus
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Dicharax notus
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Syntypes
NHMUK 1903.7.1.3065 from Fort Stedman (15 shells; Fig.
Shell small (SH up to 2.2 mm, SW up to 3.6 mm), depressed-conical. Spire ca. 1/5 of shell height. R1 with regular ribs; R2 as long as or shorter than R3; R2 with 48–50 ribs. R3 with low blunt central swelling, more elevated in newly examined population. Aperture round. Inner peristome without indentation, with parieto-columellar angle in newly examined population. Outer peristome expanded, reflected. Umbilicus round. Operculum multispiral either with or without elevated lamella.
Shan State, Myanmar (
Similar to D. cristatus (Möllendorff, 1886) from China and Vietnam as well as D. depressus (Bavay & Dautzenberg, 1912) and the rounded peristome morph of D. fimbriatus (the latter two known from Pac Kha, northern Vietnam) in shell size and shape, length of R2 and R3, and position of the swelling in R3 (
Alycaeus omissus Godwin-Austen, 1914: 411, pl. 155, fig. 13. Type locality: Siam and Shan State boundary.
Alycaeus (Chamalycaeus) omissus
–
Dicharax
(?) omissus –
Syntypes
NHMUK 1903.7.1.1228 from Siam & Shan boundary (2 shells; Fig.
Shell very small (SH up to 1.7 mm, SW up to 2.7 mm), depressed-conical. Spire ca. 1/4 of shell height. R1 with regular, strong ribs; R2 shorter than R3; R2 with 35–36 ribs. R3 with blunt central swelling. Aperture round. Inner peristome without indentation, with beak-like basal protrusion in newly examined population. Outer peristome expanded, not reflected. Umbilicus round.
Border region between Thailand and Myanmar (
The specimen from Mae Hong Son Province (Fig.
Alycaeus pratatensis Panha & Burch, 1997: 119–122, fig. 2a–c. Type locality: “Tham Pratat, Erawan National Park, Kanchanaburi Province, Thailand”, hereby emended to: “Doi Chiang Dao, Chiang Mai Province, Northern Thailand”.
Holotype
Shell small (SH up to 2 mm, SW up to 3.2 mm), depressed-conical. Spire ca. 1/6 of shell height. R1 with regular, very strong ribs; R2 shorter than R3; R2 with 44–51 ribs. R3 with prominent, blunt swelling near aperture, anterior slope of swelling steeper than posterior slope. Aperture round. Inner peristome thickened, protruding, with slight parieto-columellar angle. Outer peristome expanded, not reflected. Umbilicus round. Operculum multispiral.
Known only from Doi Chiang Dao, Chiang Mai Province, Thailand.
Re-examination of the type materials (holotype Cy 001: Fig.
Holotype
Synoptic view of the eight Dicharax taxa in Thailand. A. Dicharax omissus, specimen
Shell medium-sized (SH up to 2.7 mm, SW up to 4.4 mm), depressed-conical. Spire ca. 1/6 of shell height. R1 with regular ribs; R2 twice longer than R3; R2 with ca. 72 ribs. R3 with very low, elongated swelling. Aperture oval. Inner peristome thickened, with three very shallow indentations, always without parieto-columellar indentation. Outer peristome expanded, not reflected. Umbilicus round.
Shell medium-sized (SH up to 2.7 mm, SW up to 4.4 mm), depressed-conical, solid, translucent, pale yellowish. Shell outline oval in apical view, spire ca. 1/6 of shell height. Whorls ca. 4¼. Protoconch low, ca. two whorls, glossy and smooth. R1 ca. 1¾ whorls, with fine, regular ribs; with ca. 21 ribs in ¼ whorl adjoining R2, ribs sharper near suture and inside umbilicus than in middle of body whorl. Boundary between R1 and R2 distinct as R2 contains more close-set and thicker ribs than R1; R2 with ca. 72 ribs that are curved towards aperture; R2 ca. 1/3 whorl and twice longer than R3. Boundary between R2 and R3 distinct due to shallow constriction; R3 with fine growth lines; with very low and elongated swelling. Aperture oval; slightly oblique to shell axis. Peristome double with regular outer peristome. Inner peristome thick, expanded, with three very shallow indentations, always without parieto-columellar indentation. Outer peristome thinner, expanded, not reflected, multi-layered (visible mostly in lateral view). Umbilicus round, open, approximately one third of shell width. Operculum unknown.
The specific epithet “borealis” refers to the occurrence of the new species from the northern mountain of Thailand.
Known only from the type locality in Chiang Mai Province, Thailand.
Differs from the sympatric D. cucullatus in having a wider shell, a rather oval outline, a shorter R3 with very low and elongated swelling, a less fringed and oval aperture and an inner peristome with three very shallow indentations, always without any parieto-columellar indentation.
Holotype
Shell small (SH up to 3.6 mm, SW up to 3.5 mm), conical. Spire ca. ½ of shell height. R1 with regular, strong ribs; R2 as long as R3; R2 with 36–43 ribs. R3 with either sharp and narrow or blunt and more elongated swelling in the middle of R3 or near aperture. Aperture round. Inner peristome blunt, slightly protruding. Outer peristome expanded (most conspicuously at the upper palatal position and near the umbilicus), reflected. Umbilicus partly or entirely covered by expanded outer peristome. Operculum multispiral.
Shell small (SH up to 3.6 mm, SW up to 3.5 mm), conical, solid, semitransparent, yellowish to pale orange. Shell outline round in apical view, spire ca. ½ of shell height. Whorls approaching 5, last whorl large. Protoconch low, ca. two whorls, glossy and smooth. R1 ca. 2 whorls, with regular, strong ribs; with ca. 21 ribs in ¼ whorl adjoining R2, ribs sharper near suture and flatter near umbilicus, most prominent when approaching R2. Boundary between R1 and R2 distinct as R2 contains more close-set ribs than R1; R2 with 36–43 ribs that are curved towards aperture; R2 ca. ¼ whorl, as long as R3. Boundary between R2 and R3 distinct due to shallow constriction; R3 smooth with indistinct growth lines; with either sharp and narrow or blunt and more elongated swelling in the middle of R3 or near aperture. Aperture round; slightly oblique to shell axis. Peristome double with prominent outer peristome. Inner peristome blunt, slightly protruding. Outer peristome strongly thickened, expanded, reflected, most conspicuously at the upper palatal position and near the umbilicus, multilayered (visible in lateral view). Umbilicus is partly or entirely closed by the reflected outer peristome. Operculum thin; multispiral ridges not significantly elevated.
In honor of Prof. John B. Burch, a prominent American malacologist, who, together with Prof. S. Panha, extensively studied the taxonomy and systematics of micro land snails of Thailand.
The new species is known from the type locality, Tham Phaya Nakharat, Khon Kaen Province, Northeastern Thailand. The other localities are Doi Chiang Dao, Chiang Mai Province and Ban Soppong, Mae Hong Son Province, Northern Thailand, and also from Shan State, Myanmar.
Differs from D. vestitus (Blanford, 1862) from Moditoung [Modi Taung, Arakan Hills] (Fig.
A. Dicharax burchi sp. nov., specimen HA (locality code: 2018/41) from Hsihseng centre E ca. 6 km, limestone hill, Shan State, Myanmar; B. Dicharax vestitus, holotype NHMUK 1906.4.4.53; C. Dicharax vestitus akyabensis, syntype NHMUK 1888.12.4.251–252; D. Dicharax conicus, syntype NHMUK 1903.7.1.2674. Photo:
This species exhibits the variation of R1 sculpture from nearly smooth (Fig.
Dicharax pratatensis
–
Holotype
A–C. Dicharax panhai sp. nov. A. Holotype
Shell small (SH up to 2.4 mm, SW up to 3.1 mm), depressed-conical with triangular dorsal side and widened, sigmoid last whorl. Spire ca. 1/3 of shell height. R1 with regular, thread-like ribs; R2 twice shorter than R3; R2 with ca. 18 ribs. R3 with blunt central swelling. Aperture round. Inner peristome thick, protruding. Outer peristome expanded, not reflected. Umbilicus elliptical.
Shell small (SH up to 2.4 mm, SW up to 3.1 mm), depressed-conical with triangular dorsal side and widened, sigmoid last whorl; solid, worn out white; the exact color of non-weathered (fresh) shells unknown. Shell outline oval in apical view, spire ca. 1/3 of shell height. Whorls ca. 4 and 1/8. Protoconch low, ca. two whorls, glossy and smooth. R1 ca. 1¾ whorls with fine, regular, thread-like ribs; with ca. 14 ribs in ¼ whorl adjoining R2, ribs sharper near suture and flatter near umbilicus. Boundary between R1 and R2 distinct as R2 contains more close-set ribs than R1; R2 with ca. 18 ribs that are curved towards aperture; R2 ca. 1/8 whorl, twice shorter than R3. Boundary between R2 and R3 distinct due to shallow constriction; R3 initially coils horizontally forming a flat base, but aperture strongly descent being strongly oblique to shell axis; R3 mostly smooth with indistinct growth lines that become stronger near aperture; with blunt central swelling. Aperture round; slightly oblique to shell axis. Peristome double with regular outer peristome. Inner peristome thick, protruding. Outer peristome slightly expanded, not reflected, multi-layered (visible mostly in lateral view). Umbilicus elliptical, open, slightly more than one third of shell width. Operculum unknown.
In honor of Prof. Somsak Panha, a prominent Thai malacologist and our beloved professor who initiated the taxonomic and systematic study of land snails and other terrestrial invertebrates in Thailand and surrounding areas of mainland Southeast Asia.
The new species is known only from the type locality in Kanchanaburi Province, Thailand.
Similar to D. pratatensis from Doi Chiang Dao, Chiang Mai Province, Thailand in having a depressed-conical shell shape and R3 with blunt swelling, but differs in having a conical apical part on a wide shell base, less distinct ribs of R1 and shorter R2 with less ribs. The short R2 and breathing tube is also exhibited in D. abdoui Páll-Gergely in
Holotype
Shell medium-sized (SH up to 2.3 mm, SW up to 4.4 mm), lenticular, depressed-conical. Spire ca. ¼ of shell height. R1 with regular, thread-like ribs; R2 three times longer than R3; R2 with ca. 76 ribs. R3 strongly reduced, without swelling. Aperture round. Inner peristome with two shallow indentations. Outer peristome expanded, slightly reflected. Umbilicus elliptical. Operculum multispiral, with or without elevated lamella.
Shell medium-sized (SH up to 2.3 mm, SW up to 4.4 mm), lenticular, depressed-conical, solid, translucent, yellowish to pale orange. Shell outline oval in apical view, spire ca. ¼ of shell height. Whorls ca. 4 and 1/8. Protoconch low, ca. two whorls, glossy and smooth. R1 ca. 1¾ whorls with fine, regular, thread-like ribs; with ca. 17 ribs in ¼ whorl adjoining R2, ribs more elevated and sharper near suture and flatter near umbilicus and at the edge of body whorl. Boundary between R1 and R2 distinct as R2 contains denser and thicker ribs than R1; R2 with ca. 76 ribs that are curved towards aperture; R2 ca. 1/3 whorl, three times longer than R3. Boundary between R2 and R3 distinct due to shallow constriction; R3 strongly reduced, without swelling, practically the constriction continues directly to outer peristome. Aperture round; slightly oblique to shell axis. Peristome double with regular outer peristome. Inner peristome slim, slightly protruding, with two shallow indentations. Outer peristome thickened, expanded, slightly reflected, multilayered (visible in lateral view). Umbilicus elliptical, open, approximately one third of shell width. Operculum either thin with low lamella or thick with elevated lamella.
In honor of Pongrat Dumrongrojwattana, a Thai malacologist who has studied micro land snails of Thailand and was one of the collectors of this new species.
The new species is known only from the type locality in Chiang Mai Province, Thailand.
Differs from the sympatric and similar depressed-conical D. pratatensis in having a wider and more depressed shell, a much longer R2, a shorter R3 without a swelling and two shallow indentations at the inner peristome.
Dicharax species inhabiting China, Laos and Vietnam have been revised recently by
The alycaeid shell is complicated mostly due to the three clearly distinguishable regions of the teleoconch (R1, R2, R3) having their own characteristics of sculpture (the most important is the rib density), length and morphology. Previous revisions (
The recent alycaeid revisions (
Comparison of diagnostic conchological characters among Dicharax species in this study.
Species | Shell shape | Spire to shell height ratio | R2 length compared to R3 | No. of R2 ribs | Swelling of R3 | Aperture shape | Outer peristome | Inner peristome | Umbilicus |
---|---|---|---|---|---|---|---|---|---|
D. cucullatus | depressed-conical | ~1/5 | ≥ R3 | 49–57 | sharp; near aperture | round | fringed, slightly reflected but not conspicuous | with four to five indentations, always with parieto-columellar; sometimes weak at basal | round |
D. notus | depressed-conical | ~1/5 | ≤ R3 | 48–50 | low blunt; central; more elevated in newly examined population | round | expanded, reflected | without indentation; with parieto-columellar angle in newly examined population | round |
D. omissus | depressed-conical | ~1/4 | < R3 | 35–36 | blunt; central | round | expanded, not reflected | without indentation; with beak-like basal protrusion in newly examined population | round |
D. pratatensis | depressed-conical | ~1/6 | < R3 | 44–51 | prominent, blunt; near aperture; anterior slope steeper than posterior slope | round | expanded, not reflected | without indentation; with slight parieto-columellar angle | round |
D. borealis sp. nov. | depressed-conical | ~1/6 | > R3 | ~72 | very low and elongated | oval | expanded, not reflected | with three very shallow indentations, always without parieto-columellar | round |
D. burchi sp. nov. | conical | ~1/2 | ~ R3 | 36–43 | sharp and narrow or blunt and more elongated; central or near aperture | round | expanded, reflected, most conspicuously at the upper palatal position and near the umbilicus | without indentation | partly or entirely covered by expanded outer peristome |
D. panhai sp. nov. | depressed-conical with triangular dorsal side | ~1/3 | twice shorter than R3 | ~18 | blunt; central | round | expanded, not reflected | without indentation | elliptical |
D. pongrati sp. nov. | lenticular, depressed-conical | ~1/4 | three times longer than R3 | ~76 | not swelling | round | expanded, slightly reflected | with two shallow indentations | elliptical |
One population of D. cucullatus from Doi Ang Khang, Chiang Mai Province, Thailand exhibits the spiral striation on R1 (Fig.
The variation on the exterior sculpture of the operculum has been rarely recorded.
The body coloration of living specimen has been scarcely reported compared to the shell color. Living specimens of both D. cucullatus (Fig.
The authors are grateful to all members of the Animal Systematics Research Unit members, Chulalongkorn University for their kind help during field trips in Thailand, and especially to S. Panha, J.B. Burch and P. Dumrongrojwattana for the collections from northern Thailand. We are also indebted to J. Ablett, F. Naggs and H. Taylor (