The operculate micro land snail genus Dicharax Kobelt & Möllendorff, 1900 (Caenogastropoda, Alycaeidae) in Thailand, with description of new species

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.


Introduction
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 Páll-Gergely et al. (2016). This taxon has been treated as a subfamily of Cyclophoridae by several authors including Bouchet et al. (2017), whereas it has been treated as a family of its own by other sources (e.g. Egorov 2013). Based on the unique gas exchange system of the shell and the presence of synapomorphic genital anatomical characters, Páll-Gergely et al. (2020b) proposed to treat this taxon at the family level, which is followed here. This family ranges from western India to Japan, including Indonesia in the south. This group is known to be particularly diverse in three regions, (1) the southeastern Himalaya, (2) Peninsular Malaysia and Sumatra, and (3) northern Vietnam, northern Laos and southern China , 2020b, Aravind and Páll-Gergely 2018, Páll-Gergely 2019, Sajan et al. 2020. In Southeast Asia, alycaeid taxa from Laos, Vietnam, and Peninsular Malaysia have received attention in the past few years (Foon andLiew 2017, Páll-Gergely et al. 2017), whereas the taxa from Thailand have remained poorly studied. Eleven alycaeid species were described from Thailand before 2010, mostly classified as members of Alycaeus Baird, 1850(BEDO 2017; Table 1). However, reports of some species in the checklist of Thai land snails (Solem 1966, Hemmen andHemmen 2001) are questionable as these were listed without illustrations to confirm their correct identification (i.e. Dicharax diplochilus (Möllendorff, 1887), Dicharax fimbriatus (Bavay & Dautzenberg, 1912) and Dioryx bacca (Pfeiffer, 1863)).
to a full genus and questioned the conspicuous hollow ridge (termed swelling by Godwin-Austen 1914 and as feature diagnostic of the genus, and defined Dicharax as having a low protoconch and lacking spiral striation on the entire shell. Dicharax caudapiscis Páll-Gergely & Hunyadi, 2018 and D. stuparum Páll-Gergely & Hunyadi, 2018 were described from Northern Thailand subsequently (Páll-Gergely and Hunyadi 2018). Following the genus definition of , as many as 164 nominal species were assigned to Dicharax, including three Alycaeus species that were formerly recorded from Thailand or "Siam", namely A. davisi Godwin-Austen, 1914, A. omissus Godwin-Austen, 1914, and A. pratatensis Panha & Burch, 1997(Páll-Gergely et al. 2020b).
In the present paper, based on the examination of the CUMZ collections, the type locality of D. pratatensis has to be amended. The specimens from Pratat Cave, Kanchanaburi, western Thailand (the former type locality of A. pratatensis), are now described as a new species. Three additional species are also new to science and described from northern and northeastern Thailand. We also provide diagnoses to three nominal species based on the types and newly examined populations.

Material and methods
This study is based on material collected from throughout Thailand since 1996 which is now deposited in the collection of the Chulalongkorn University (CUMZ) (Fig. 1). Additional specimens from HA and UF were examined by BP-G. Live specimens were mostly collected from crevices in limestone outcrops, while empty shells were collected from the ground. Shells were measured using digital (scanning electron microscope) SEM images. The counting of the shell whorls (to the closest 1/8 whorl) follows Kerney and Cameron (1979). The nomenclature of external alycaeid shell features follows . The teleoconch is divided into three regions, namely; R1 (the beginning of the teleoconch to the beginning of the differently ribbed region along the suture), R2 (the differently ribbed area to the constriction) and R3 (the constriction to the peristome) (see Páll-Gergely et al. 2017: fig. 1a, b). The swelling on R3 is classified into either blunt (R3 gradually swollen; Páll-Gergely et al. (2017: fig. 2q)) or sharp (R3 abruptly swollen and the swelling is narrower and more elevated;   fig. 2r)). The peristome is double, and its two parts are termed "inner peristome" or "inner lip" and "outer peristome" or "outer lip" based on Liew et al. (2014: fig. 10)   Other abbreviations SH, shell height; SW, shell width.
Remarks. This species was originally described from Shan State and diagnosed by its fringed peristome with five indentations (Theobald 1870). Later, Godwin-Austen (1914) described Alycaeus davisi with a less fringed peristome with four indentations from Siam and Shan State boundary. Upon examining the type specimens, both species agree in having a depressed-conical shell shape, a long R2 and a sharp swelling of R3 near the aperture ( Fig. 2A, B). The types of A. cucullatus differ from those of A. davisi in having a more fringed peristome and more indentations. However, based on recently collected specimens, we conclude that this variation is to be interpreted as intraspecific as we found that this crenulation may vary even within the same population from nearly smooth (Fig. 4A) via slight (Fig. 4B) to strong (Fig. 2C, D). Because both species were described from the same geographical region, Alycaeus davisi is herein regarded as a junior subjective synonym of Alycaeus cucullatus. Refer to Discussion regarding the color of living specimen and variation in spiral striation.
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  Diagnosis. 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.
Remarks. 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 (Páll-Gergely et al. 2017). The specimens from Nan Province, Thailand ( Fig. 4D) differ from the type specimens in having a longer R3, a more shouldered R3 swelling, a stronger descending aperture, and a parieto-columellar angle. Despite those differences, we preliminarily identified the specimens from Nan Province as D. notus. Refer to Discussion regarding the color of living specimen and variation in operculum morphology.  Diagnosis. 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.
Remarks. The specimen from Mae Hong Son Province (Fig. 8B) exhibits stronger R1 ribs and possesses a beak-like protrusion at the base of the aperture, which is absent in the syntype (Fig. 8A). Apart from these differences, this specimen is nearly identical to the syntype in terms of shell size and shape, and R2 and R3 length. In addition, the locality of this specimen lies only approximately 12 km from the boundary between Thailand and Shan State, Myanmar. We thus identify this specimen as D. omissus. The most similar species to D. omissus is D. notus, which is larger and has reflected outer peristome. Diagnosis. 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.
Remarks. Re-examination of the type materials (holotype Cy 001: Fig. 8C and paratypes Cy 002: Fig. 8D) deposited in CUMZ and figured in the original description (Panha and Burch 1997: fig. 2) revealed that the locality code associated with the types points to "Doi Chiang Dao". However, the locality of the paratypes of Alycaeus pratatensis deposited in SMF (inv. number: 331452) appears as "Tham Pratat, Erawan National Park, Kanchanaburi Province". After we compared all the type materials to the same specimen lots of both localities housed in the general CUMZ collections and communicated with S. Panha, it became evident that the type material might have been mis-allocated. We conclude that the published type locality of A. pratatensis (Tham Pratat, Erawan National Park, Kanchanaburi Province, Thailand) is incorrect, and another species (Dicharax panhai sp. Type material. Holotype CUMZ 5072/1 (Fig. 9), paratypes CUMZ 5072/2 (2 shells; Fig. 6G Description. 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.
Etymology. The specific epithet "borealis" refers to the occurrence of the new species from the northern mountain of Thailand.
Distribution. Known only from the type locality in Chiang Mai Province, Thailand.

Dicharax burchi
Other material examined. UF 347279 from limestone pass 10.0 km NW Ban Soppong, Mae Hong Son Province, Thailand, 19°33.183'N, 98°11.533'E, 800 m a.s.l., Diagnosis. 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.
Description. 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.
Etymology. 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.
Distribution. 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.
Remarks. Differs from D. vestitus (Blanford, 1862) from Moditoung [Modi Taung, Arakan Hills] (Fig. 11B), and its subspecies D. v. akyabensis (Godwin-Austen, 1914) from Baumi, Akyab [Sittwe] (Fig. 11C), both from Rhakhine State, Myanmar, by having a smaller shell with a higher spire, a longer last whorl and a less distinct and a narrower constriction between R2 and R3. Differs from D. conicus (Godwin-Austen, 1871) from Samiamri, E of the Kopili R., Assam State, India (Fig. 11D) in having a longer last whorl, more close-set ribs on R2, and the inner and outer peristomes are narrower and less reflected. Differs from D. imitator Páll-Gergely & Hunyadi in Páll-Gergely et al., 2017 from Guangxi, China in having a less smooth R1, a much thicker peristome, a longer R2, a shallower constriction between R2 and R3, the last whorl less oblique compared to the columellar axis and a less triangular aperture .

Dicharax panhai
Description. 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 peri-stome. 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. Etymology. 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.
Distribution. The new species is known only from the type locality in Kanchanaburi Province, Thailand.
Remarks. 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 Páll-Gergely et al., 2017 from Khammouane Province, Laos and D. stuparum from Chiang Rai Province, Northern Thailand, but D. panhai sp. nov. is larger, comprises more whorls, has a more elevated spire and a larger last whorl ( Diagnosis. 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.
Description. 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.
Etymology. 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.
Distribution. The new species is known only from the type locality in Chiang Mai Province, Thailand.
Remarks. 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.

Discussion
Dicharax species inhabiting China, Laos and Vietnam have been revised recently by . Several other species have been included in Dicharax in a recent family-wise revision without examining species-level taxonomy (Páll-Gergely et al. 2020b). Here we report a total of ten Dicharax species from Thailand, six out of ten species being recorded from their type localities only, and the remaining species with additional occurrences within the vicinity of the type locality which ranges wider within Thailand or both Thailand and Myanmar. Nearly all Dicharax species are known from the northern mountainous region except for D. panhai sp. nov., the type locality of which is in the Tenasserim Range.    In addition, the populations here assigned to D. burchi sp. nov. inhabit a wide area from Myanmar to northeastern Thailand (Fig. 1) and shows considerable variation in terms of shell characters. Nevertheless, we currently refrain from describing local populations as subspecies.
The disjunct distribution of Dicharax species has been reported in D. diminutus (Heude, 1885) from China, whereas some species, e.g. D. fimbriatus and D. cristatus, show a wide distribution range from China to Vietnam and Laos (Páll-Gergely et al. 2017). Additional, especially molecular phylogenetic analyses could reveal that the morphologically distinct populations currently treated as a single species might represent distinct species.
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 , 2020b, Páll-Gergely and Auffenberg 2019 showed that most populations are recognizable, i.e. possess unique combinations of characters that distinguish them from other conspecific populations. Due to the high variability among populations, the most useful approach is being a lumper, in order not to over split the alycaeid genera and not to describe many unrealistic species (Páll-Gergely et al. 2020b: 27). Thus, instead of describing every recognizable population as distinct species (or even subspecies), we only distinguish species with unique character states, and attempt to apply existing nominal species to newly examined populations as much as possible. The latter is the situation for D. notus and D. omissus, which have so far been known from single populations. The populations we examined and identified as D. notus and D. omissus, differ from their respective type specimens in some characters, which we interpret as being insufficient for distinguishing them at species level. Moreover, both species are variable and widespread, as revealed by the examination of additional populations from Thailand and Myanmar (Páll-Gergely et al. in prep.).
The recent alycaeid revisions (Páll-Gergely et al. 2017, Páll-Gergely and Auffenberg 2019) also showed that most important characters to distinguish species are the relative lengths of regions (especially R2 and R3) and the general shell shape, whereas other characters, such as the shape of swelling on R3, and the crenulation and protrusion of outer peristome, show large intraspecific variability (although they can be useful in some cases to distinguish species). The new species described here are recognized based on the following characters (Table 2): (1) Dicharax burchi sp. nov. is recognized by its conical shell shape with an elevated spire, even if the examined populations show variation in terms of rib strength and density, the shape of R3 swelling and the expansion of the outer peristome; (2) Dicharax panhai sp. nov. has a unique shell shape of a wide base and triangular dorsal side, and a short R2; (3) Dicharax pongrati sp. nov. has a lenticular, depressed-conical shell shape, an extremely long R2 and a very short R3; (4) Dicharax borealis sp. nov. has a depressed-conical shell shape, a very low and elongated R3 swelling and an inner peristome with three very shallow indentations. Although D. borealis sp. nov. could be interpreted as a D. cucullatus with a low R3 swelling, it is sympatric with a D. cucullatus population at the type locality of D. borealis sp. nov., which excludes conspecificity.
One population of D. cucullatus from Doi Ang Khang, Chiang Mai Province, Thailand exhibits the spiral striation on R1 (Fig. 2C, D). The spiral striation was rarely found in Dicharax and was reported in very few species (e.g. D. candrakirana Nurinsiyah & Hausdorf, 2017, one population of D. depressus). In those cases, the spiral striation is probably the part of lower shell layers and assumed not to be homologous with those of Chamalycaeus and Metalycaeus species , 2020b. However, in this case the normal spiral striation which is elevated from the shell surface found in one D. cucullatus population could be regarded as homologous to the condition found in the other genera.
The variation on the exterior sculpture of the operculum has been rarely recorded. Foon and Liew (2017) noted the discrepancy of the operculum of two species, Stomacosmethis roebeleni (Möllendorff, 1894) and Pincerna thieroti (Morgan, 1885), between the original description and recently examined specimens. The original descriptions of both species described the opercula as entirely non-calcified (Morgan 1885, Möllendorff 1894, while the recently examined specimens exhibit the opercula with calcified exterior layers (Foon and Liew 2017). Moreover,  reported the variation from an operculum without elevated lamella to the presence of elevated lamella in D. cristatus, D. depressus and D. fimbriatus, and from smooth to multispiral (i.e. with low lamella) opercula in D. fraterculus (Bavay & Dautzenberg, 1900). However, these differences were compared between specimens from different localities. The only report about variation (presence or absence of the elevated lamella) within the same population was reported in Metalycaeus nipponensis (Reinhardt, 1877) (Páll-Gergely et al. 2020b). Here we first report the variation of the outer opercular surface in the same population in Dicharax, which is illustrated in D. notus in possessing an operculum either without (Fig. 7A) or with an elevated lamella (Fig.  7B). We thus suggest that this trait might be less advantageous in diagnosing different Dicharax species, and probably in other alycaeid genera.
The body coloration of living specimen has been scarcely reported compared to the shell color. Living specimens of both D. cucullatus (Fig. 5A) and D. notus (Fig. 5B) have a reddish orange shell with a pink apex and a light-yellow to pale orange body coloration. In addition, most Dicharax shells in this study have a reddish orange shell (Fig. 6). Comparing to other alycaeid species, Stomacosmethis somnueki (Panha & Patamakanthin, 2001) has a white, bright yellow or orange shell and a pale yellow body color (Panha and Patamakanthin 2001), whereas several species of Alycaeus, Pincerna and Stomacosmethis species from Peninsular Malaysia have a yellow shell with an orange apex and a pale yellow to gray body color (Foon and Liew 2017). The shell coloration could be used to classify some alycaeid genera to some extent. Stomacosmethis is usually bright yellow or orange, and Alycaeus is more colorful with reddish or yellowish tint compared to Chamalycaeus which has a similar shell but colorless (Páll-Gergely et al. 2020b). However, the light-yellow to pale orange body coloration is common, often associated with lighter colored shell and might not be different among genera.