Diplommatinidae, L. Pfeiffer, 1856

YAMAZAKI, KAZUNORI, YAMAZAKI, MIDORI & UESHIMA, REI, 2013, <p> <strong> Systematic review of diplommatinid land snails (Caenogastropoda, Diplommatinidae) endemic to the Palau Islands. (1) Generic classification and revision of <em> Hungerfordia </ em> </ strong> <br /> <strong> species with highly developed axial ribs </ strong> </ p>, Zootaxa 3743 (1), pp. 1-71 : 15-21

Family Diplommatinidae

Genus Palaina Semper, 1865

Type species. Diplommatina macgillivrayi Pfeiffer, 1854 by subsequent designation of Iredale (1944).

Palaina in part: Semper, 1865, p. 291.

Diplommatina (Palaina) in part: Pfeiffer, 1876b, pp. 89–90, pp. 397–403.

Palaina in part: Kobelt & Moellendorff, 1898, pp. 131–134.

Palaina in part: Kobelt, 1902, pp. 393–406.

Palaina: Thiele, 1929, p. 109 .

Palaina: Wentz, 1939, pp. 481–482 .

Palaina: Benthem Jutting, 1948, pp. 585–587 .

Palaina in part: Solem, 1959, pp. 190–194.

Palaina: Vermeulen & Whitten, 1998, pp. 51–53 .

Diagnosis. Shell mostly sinistral, occasionally dextral. Shell shape fusiform, cylindrical, pupiform, or conical. Axial ribs generally present on the teleoconch, low, never highly protruded as wings nor spines, almost straight, never folded at the periphery. Spiral sculptures present or absent. Constriction located above the aperture, internally without parietal or columellar tooth, without palatal plica except a low, axial-crest. Columellar tooth generally absent, occasionally present but weak, never deeply extended inward. Tuba c.a. 3/4 whorls, never decoiled nor reversed as in Opisthostoma . Umbilicus closed in adult. Peristome double or single.

Operculum corneous, multispiral, frequently concave; with an arcuate ridge on the inner surface; frequently with spiral ridge on the outer surface.

Radula taenioglossate, typical of cyclophoroideans. Central tooth of normal size, with a small central cusp, with 2–3 pairs of developed lateral cusps. Lateral teeth with 4 developed cusps. Inner and outer marginal teeth with 3–5 cusps.

Remarks. Although Palaina is one of the major and “common” genera of diplommatinid, along with Diplommatina , the generic concept has been poorly defined. Palaina has long been distinguished from Diplommatina by the absence of a columellar tooth within the aperture ( Semper 1865; Kobelt 1902; Thiele 1929; Wentz 1939). The traditional delimitation, however, became obscured by the discovery of some Palaina species that have a columellar tooth ( Solem 1960; Tillier 1981). Tillier (1981) doubts the taxonomic significance of this character and validity of generic separation.

Palaina and Diplommatina are distinct genera in fact. We confirmed that the traditional delimitation remains still useful in most cases, and that some “problematic” species with a weak columellar tooth may be classified into one of the two genera by examining additional characters. In Diplommatina , the columellar tooth is strongly developed and deeply extended inward, almost reaching the constriction. In contrast, in Palaina , the columellar tooth, which is usually absent, is weak and short, never extends deeply, even when present. More importantly, Diplommatina also differs from Palaina with respect to the development of a parietal tooth and longitudinal (spiral) palatal plicae inside the constriction. The internal tooth and plicae are absent in Palaina , but are usually well developed in Diplommatina . Furthermore, Palaina has a characteristic operculum with an arcuate ridge on the inner surface. The presence of an arcuate ridge inside the operculum was first reported by Tillier (1981) for P. macgillivrayi from Lord Howe Island and New Caledonian Palaina species. This character was validated as a diagnostic character of the genus in this study. Vermeulen (1996) suggested another operculum character to be diagnostic for the genus; specifically, the presence of a spiral ridge on the outer surface, based on two Palaina species from Bali, Indonesia. We confirmed that the latter operculum character is also typical of the genus, although the spiral ridge is occasionally reduced in some Palaina species ( Figs. 10A–C ). In contrast, in Diplommatina , both the inner and outer sides of the operculum are always smooth, and thus easily distinguishable from those of Palaina . Therefore, Palaina is redefined here based on shell and operculum characters. Many diplommatinids from the Pacific islands and South-east Asia have been arbitrarily classified into either Palaina or Diplommatina based on the development of the columellar tooth alone. The generic status of these diplommatinids should be revised based on the inner shell structure and operculum morphology.

Subgenus Eupalaina Kobelt & Moellendorff, 1898

Type species. Palaina patula Crosse, 1866 by subsequent designation in this paper.

Palaina in part: Semper, 1865, p. 291.

Diplommatina in part: Pfeiffer, 1876a, pp. 15–24.

Diplommatina (Palaina) in part: Pfeiffer, 1876b, pp. 89–90, pp. 397– 403.

Palaina (Eupalaina) in part: Kobelt & Moellendorff, 1898, pp. 131–134.

Palaina (Cylindropalaina) in part: Kobelt & Moellendorff, 1898, p. 133.

Palaina (Palaina) in part: Kobelt, 1902, pp. 393–406.

Palaina (Cylindropalaina) in part: Kobelt, 1902, pp. 406–409.

Palaina (Palaina) in part: Thiele, 1929, p. 109.

Palaina (Palaina) in part: Wentz, 1939, pp. 481–482.

Palaina (Cylindropalaina) in part: Wentz, 1939, p. 482.

Diagnosis. Shell sinistral. Shell color usually reddish brown, occasionally white, rarely yellow. Shell shape generally fusiform, cylindrical or pupiform, rarely spherical or conical. Protoconch punctated. Axial ribs generally present on the teleoconch, low, never highly protruded as wings or spines, almost straight, never folded at the periphery. Spiral sculptures generally present on the teleoconch, occasionally reduced. Constriction located above the aperture, frequently (but not always) followed by a prominent swelling of whorl, internally without parietal tooth, without palatal plicae or lamellae except a low axial-crest caused by the constriction. Columellar tooth generally absent, but occasionally present, weak and short. Tuba c.a. 3/4 whorls, never decoiled nor inverted. Umbilicus closed in adult. Aperture hardly to slightly protruded. Peristome double or single.

Operculum corneous, thick, concave, multispiral, with a strong and highly protruded arcuate ridge on the inner surface, occasionally with spiral ridge near the margin on the outer surface.

Radula taenioglossate, typical of cyclophoroideans. Central tooth of normal size, with a rather small central cusp, with 2–3 pairs of developed lateral cusps; basal plate laterally elongated, rectangular. Lateral teeth with a normal-sized major cusp, with two developed inner cusps, with a small outer cusp; basal plate obliquely elongated. Inner marginal teeth with a major cusp, with two developed inner cusps, with 1–2 smaller outer cups. Outer marginal teeth with a major cusp, with three inner cusps (two larger cusps similarly developed as major one, and a small innermost cusp which is usually hidden by the larger inner cusp), with a rather large, almost right-angled, outer cusp which locates a short distance below the major one. Radular ribbon of usual length. Radular sac small.

Penis present in male.

Ecology. Palauan Palaina species inhabit wet leaf litter, and are occasionally found on the underside of limestone rocks. They inhabit both limestone and volcanic (non-limestone) soils.

Remarks. When Semper (1865) proposed the genus Palaina , just 15 species were listed, without the type species being designated. The selection of a Palauan species, P. patula , as the “representative of the genus” was later proposed by Kobelt (1902), and followed by Thiele (1929). Wenz (1953) stated that P. patula is the type species of the genus. Iredale (1944), however, pointed out that the name P. patula was not available when Semper (1865) established the genus, even though P. patula was formally described in the subsequent year by Crosse (1866). Iredale (1944) re-designated the type species of the genus as P. macgillivrayi Pfeiffer, 1854 from Lord Howe Island. As Iredale’s (1944) subsequent designation is valid according to the International Code of Zoological Nomenclature, the type species of the genus Palaina was changed from a Palauan species, P. patula , to an Australian species, P. macgillivrayi .

The morphological features of the shell, operculum, and radula of Palauan Palaina species are consistent with those of the genus, particularly those of the type species, P. macgillivrayi ( Tillier 1981; Yamazaki & Ueshima unpublished data). Nevertheless, Palauan Palaina species have a unique genital character, which distinguishes them from other congeners. A penis is present in all Palauan species, whereas the penis is absent in the type species and New Caledonian congeners ( Tillier 1981). On the basis of the genital difference, which warrants supra-specific recognition, we restored the subgenus Eupalaina Kobelt & Moellendorff, 1898 for Palauan species by designating P. patula as the type species. Eupalaina was originally proposed as an absolute synonym of subgenus Palaina (sensu stricto), without determining the type species. Eupalaina is redefined here as a distinct subgenus, which differs from Palaina (Palaina) by the presence of a penis.

Among the seven subgenera of Palaina listed by Solem (1959), two subgenera were named earlier than Eupalaina Kobelt & Moellendorff, 1898 ; namely, Cylindropalaina Moellendorff, 1897 and Macropalaina Moellendorff, 1897 . These subgenera were proposed based on a trivial difference in shell shape, leading to their taxonomic validity being questioned ( Solem 1959; Tillier 1981). As anatomical information on the type species of these problematic “subgenera” is not available, the subgenus Eupalaina will be used for Palauan species, until the taxonomic relationships of these “subgenera” are clarified.

The following Palauan taxa, which were assigned to Diplommatina in some previous studies, are now placed in Palaina (Eupalaina) based on our observations of the shell, operculum, radular, and genital morphology: P. dimorpha Crosse, 1866 ; P. moussoni Crosse, 1866 ; P. patula Crosse, 1866 ; P. pupa Crosse, 1866 ; P. strigata Crosse, 1866 ; P. striolata Crosse, 1866 ; P. wilsoni Crosse, 1866 ; P. albata ( Beddome, 1889) ; P. platycheilus ( Beddome, 1889) ; P. rubella ( Beddome, 1889) ; P. strigata kororensis ( Beddome, 1889) .

Genus Hungerfordia Beddome, 1889

Type species. Hungerfordia pelewensis Beddome, 1889 by original designation.

Hungerfordia: Beddome, 1889, pp. 115–116 .

Hungerfordia: Crosse, 1892, pp. 280–282 .

Hungerfordia: Kobelt & Moellendorff, 1898, p. 135 .

Hungerfordia: Kobelt, 1902, pp. 422–423 .

Hungerfordia: Thiele, 1929, p. 110 .

Hungerfordia: Wentz, 1939, p. 483 .

Diplommatina (Pseudopalaina) in part: Moellendorff in Kobelt & Moellendorff, 1898, p. 139, synonym nov. [Type species: Palaina polymorpha Crosse, 1866 by subsequent designation of Wentz (1939)].

Diplommatina (Pseudopalaina) in part: Kobelt, 1902, pp. 451–455.

Pseudopalaina in part: Thiele, 1929, p. 111.

Pseudopalaina in part: Wentz, 1939, p. 483.

Diagnosis. Shell generally sinistral, rarely dextral, variable in size from small to very large for the family. Shell color variable from white, transparent, yellow to reddish brown, occasionally bicolored. Shell shape extremely variable from depressed conical, fusiform to slender conical with high spire. Protoconch almost smooth or punctuated to a various degree. Axial ribs developed on the teleoconch, extremely variable, highly protruded as wings or spines in some species, low or disappeared in other species, folded at the periphery or not. Spiral sculptures generally present on the teleoconch, crossing the axial ribs, occasionally reduced. Constriction usually located above the aperture, but rarely located a half whorl behind the aperture, internally without parietal tooth, without palatal plicae or lamellae except a low axial-crest caused by the constriction. Tuba usually 7/8–3/4 whorls, rarely only a half whorl, not decoiled nor inverted. Umbilicus usually closed, rarely opened in adult. Aperture hardly to strongly protruded. Columellar tooth usually present within the aperture, occasionally reduced to a various degree. Peristome double or single.

Operculum corneous, multispiral, circular, thin, flat, semi-transparent, smooth on the outer surface, with a low arcuate ridge on the inner surface.

Radula highly specialized type of taenioglossate. Central tooth unusually large, with a large, very wide and blunted central cusp, with or without 1–2 pairs of vestigial lateral cups; basal plate longitudinally elongated and strongly constricted at the base. Lateral teeth located distinctly below the central tooth, with a large, very wide and blunted major cusp, with or without a vestigial inner cusp, without outer cusp. Inner marginal teeth with a rather large major cusp, with two slender inner cusps, with a small outer cup. Outer marginal teeth with a large major cusp, with 1–2 of slender inner cusps, without outer cusp. Radular ribbon very long; proximal part forming a large coil within the swollen radular sac.

Penis absent.

Ecology. Calciphilic. Hungerfordia species exclusively inhabit the surface or underside of limestone rocks.

Distribution. Endemic to limestone areas of the Palau Islands.

Remarks. Hungerfordia has long been known as a monotypic genus ( Beddome 1889; Kobelt & Moellendorff 1898; Kobelt 1902; Thiele 1929; Wentz 1939). Rundell (2008) assigned provisionally some undescribed species with spiny ribs to the genus, for a molecular phylogenetic analysis; however, the author excluded some low-ribbed Palauan species, such as “D.” ringens and “ D.” lutea , assigning them to a different genus Diplommatina . The current redefinition of Hungerfordia expands the generic concept to include a wider range of species that exhibit highly divergent shell shapes and sculptures ( Figs. 11F–N ). The genus Hungerfordia redefined here is characterized and distinguished from all other diplommatinid genera by the following features: a highly specialized taenioglossate radula with a very long ribbon; the presence of a columellar tooth, which is occasionally reduced in some species; a thin and flat operculum, with a low arcuate ridge on the inner surface; the absence of a parietal tooth and longitudinal (spiral) palatal plicae inside the constriction; and the absence of a penis. The highly specialized taenioglossate radula of Hungerfordia is remarkable, because this type of radula is unique not only within the family Diplommatinidae but also among Cyclophoroidean families. The unusual radular features were first mentioned by Thiele (1929) in Pseudopalaina , which is now treated as a junior synonym of Hungerfordia (see discussion below), and are confirmed as unique synapomorphies of Hungerfordia (sensu lato).

Some Hungerfordia species that have a strong columellar tooth and low axial ribs, such as H. lutea and H. aurea , were placed or assigned provisionally to the genus Diplommatina ( Kobelt & Moellendorff 1898; Kobelt 1902; Rundell 2008, 2010). However, these species are not related to Diplommatina . True Diplommatina species , which are represented by continental and insular Asian species, differ from the Palauan species by the presence of a well-developed parietal tooth and longitudinal palatal plicae inside the constriction, in addition to a typical taenioglossate radula like Palaina , and the absence of an arcuate ridge on the inner surface of the operculum.

The following Palauan diplommatinids, formerly placed in Palaina or Diplommatina , are transferred to Hungerfordia in this paper, based on our observations of the radular, operculum, genital, and shell features: H. alata ( Crosse, 1866) comb. nov.; H. lamellata ( Crosse, 1866) comb. nov.; H. pyramis ( Crosse, 1866) comb. nov.; H. ringens ( Crosse, 1866) comb. nov.; H. polymorpha ( Crosse, 1866) comb. nov.; H. inflatula ( Crosse, 1866) comb. nov.; H. lutea ( Beddome, 1889) comb. nov.; H. aurea ( Beddome, 1889) comb. nov.; H. gibboni ( Beddome, 1889) comb. nov.; H. crassilabris ( Beddome, 1889) comb. nov. (see Table 1).

Pseudopalaina Moellendorff in Kobelt & Moellendorff, 1898 is the other generic taxon established for Palauan diplommatinids. Pseudopalaina was first proposed as a subgenus of Diplommatina ( Kobelt & Moellendorff 1898; Kobelt 1902). Subsequently, it was raised to full genus status ( Thiele 1929; Wenz 1939). More recently, Rundell (2008, 2010) did not mention about Pseudopalaina at all, but the author assigned provisionally the type species of Pseudopalaina , H. polymorpha , to the genus Diplommatina ( Rundell 2010) . The shell shape and sculpture of H. polymorpha , the type species of Pseudopalaina , is substantially divergent from that of H. pelewensis , the type species of Hungerfordia ( Figs. 11F, 11M, 11N ). Despite a notable dissimilarity in external shell morphology, H. polymorpha has all of the diagnostic features of Hungerfordia . These features include a highly specialized taenioglossate radula with a very long ribbon, the absence of a penis, a thin and flat operculum with a low arcuate ridge on the inner surface, the absence of a parietal tooth and longitudinal palatal plicae inside the constriction, and the presence of columellar tooth within the aperture ( Figs. 7E , 8B, 8 E 2 , 10E, 10G , 11F ). Therefore, Pseudopalaina (synonym nov.) is treated as a junior synonym of Hungerfordia , rather than Diplommatina .

Another taxonomic issue requiring discussion is whether Hungerfordia may be divided into more than one subgenus, and whether Pseudopalaina is available as a subgenus within Hungerfordia . On the basis of shell shape and sculpture, Hungerfordia species may be roughly divided into 3 morpho-types: A-, B-, and C-types. The Atype, which is represented by H. polymorpha , is characterized by a fusiform shell, low axial ribs, and a strong columellar tooth ( Fig. 11F ). The B-type, which is represented by H. alata , is characterized by a slender conical shell, highly developed ribs, and a reduced columellar tooth ( Fig. 11J ). The C-type, which is represented by a single species, H. pelewensis , is characterized by an unusually depressed conical shell, a sharp peripheral keel on the upper whorls, a body whorl that is distinctly shaped and sculptured from the upper whorls, the presence of a strong basal keel, a short tuba of only a half whorl, and an aperture that is strongly turned downward ( Figs. 11M– N ). Although these three morpho-types initially appear to represent subgroups within Hungerfordia , they cannot be clearly distinguished from each other. The A- and B-types are linked by a series of intermediates, showing a gradual development or reduction in the axial ribs and the columellar tooth ( Figs. 11F–J ). Even the C-type, the most aberrant morpho-type within the genus, is linked by several intermediates with the B-type, such as H. goniobasis goniobasis and H. elegantissima ( Figs. 11J–N ). For instance, H. goniobasis goniobasis exhibits a shell shape and sculpture that is typical of the B-type, but has a basal keel that is typical of the C-type ( Figs. 11K 1 –K 2 ); H. elegantissima also exhibits a shell shape and sculpture of the B-type, but has a short tuba of only a half whorl and a downward-directing aperture that are typical of the C-type ( Figs. 11L 1 –L 2 ). H. polymorpha and H. pelewensis , which are type species of Pseudopalaina and Hungerfordia , respectively, should thus be regarded as two extreme examples within a continuous morpho-cline, rather than representatives of divergent lineages. Accordingly, we rejected subgeneric division within Hungerfordia .

Key to the Hungerfordia species and subspecies with highly developed axial ribs

1a. Shell depressed or low conic. Periphery sharply keeled on upper whorls higher than the body whorl. Axial ribs on the last 3/4 whorls closely spaced, very low, without any spiny projection except a basal keel............ H. pelewensis Beddome, 1889

1b. Shell high conic or fusiform. Periphery rounded or obtusely angulate at most, never sharply keeled. Axial ribs on the last 3/4 whorls widely spaced, high, with highly developed spiny or wing-like projections.................................. 2

2a. Constriction located at a half whorl behind the aperture. Last 1/16–1/8 whorls decoiled downward. Spiny ribs around the constriction never reduced, similarly spaced as those on the preceding whorls. Shell diameter (including the spiny ribs) larger than the shell height, due to the very long spiny projections of the ribs............................ H. elegantissima sp. nov.

2b. Constriction located above the aperture (at 3/4–7/8 whorls behind the aperture). Last 1/16–1/8 whorls attaching to the penultimate whorl. Axial ribs around the constriction abruptly becoming closely spaced and lower, usually with greatly reduced spiny or wing-like projections. Shell diameter (including the spiny or wing-like ribs) smaller than the shell height.............. 3

3a. Basal keel present on the last whorl, continued to the outer peristome. Shell small: shell height (including outer peristome) smaller than 3.5 mm................................................................................... 4

3b. Basal keel absent. Shell large: shell height (including outer peristome) larger than 4.5 mm............................ 5

4a. Aperture small. Parietal margin of inner peristome protruded downward, shortly separated from the base of the upper body whorl. Interspace between the spiny ribs smooth below the suture. Distribution Mecherchar island........................................................................................ H. goniobasis goniobasis sp. et subsp. nov.

4b. Aperture large. Parietal margin of inner peristome attached to the base of the upper body whorl. Interspace between the spiny ribs with distinct growth wrinkles below the suture. Distribution endemic to Dmasech islet................................................................................................ H. goniobasis dmasechensis subsp. nov.

5a. Umbilicus clearly opened in adult. Wing-like ribs on apical whorls (higher than the penultimate whorl) mostly synchronized with and overlapped with those on the previous whorls........................................................ 6

5b. Umbilicus closed (opened very narrowly in rare cases) in adult. Spiny or wing-like ribs never synchronized with nor overlapped with those on the previous whorls even on apical whorls................................................. 7

6a. Synchronization of axial ribs perfectly conserved on all whorls except the last whorl. Wing-like projections of the ribs on the penultimate and antepenultimate whorls very wide, overlapped with those on the previous whorls, almost flat. Distribution Ngeruktabel island, its satellite islets, and Babelomekang island..................... H. papilio papilio sp. et subsp. nov.

6b. Synchronization of axial rib occasionally not preserved even on upper whorls. Wing-like projections of the ribs on the penultimate and antepenultimate whorls narrower, separated from those on the previous whorls, weakly folded at the periphery. Distribution Mecherchar island, its satellite islets, and Euidelchol island.................. H. papilio stenoptera subsp. nov.

7a. One or two axial palatal plica present inside the constriction. Constriction frequently followed by an abrupt whorl swelling. Shell color usually orange. Initial teleoconch, which has low and closely spaced ribs, continued for 1/3–1/2 whorls. Apical septum always absent...................................................... H. lamellata ( Crosse, 1866) comb. nov.

7b. Palatal plica absent inside the constriction, except a low axial-crest caused by the constriction. Constriction never followed by a prominent whorl swelling. Shell color usually white, occasionally yellow. Initial teleoconch, which has low and closely spaced ribs, less than 1/4 whorls, or initial teleoconch with widely spaced ribs. Apical septum present or absent........... 8

8a. Outer peristome absent: dorsal side of the inner peristome occasionally with reduced spiny ribs instead of outer peristome..................................................................................... H. nudicollum sp. nov.

8b. Outer peristome always present, strongly developed.......................................................... 9

9a. Spiny or wing-like projections of axial ribs rather narrow, arising at some distance below the suture (near periphery of a whorl) on the antepenultimate whorl........................................................................... 10

9b. Spiny or wing-like projection of axial ribs wide, arising at the suture on the antepenultimate whorl.................... 13

10a. Inner and outer peristomes fragile, very widely expanded. Interspace between the inner and outer peristomes smooth on its outer surface. Axial protrusions of shell wall (along the ribs) strongly developed on the last whorl. Columellar tooth absent.................................................................................. H. expansilabris sp. nov.

10b. Inner and outer peristomes rather stout, not so wide as 10a. Interspace between the inner and outer peristomes with some growth wrinkles, riblets, or lamellar ribs on its outer surface. Axial protrusions of shell wall (along the ribs) hardly or weakly developed on the last whorl. Columellar tooth weakly developed or reduced...................................... 11

11a. Peristome triple, with doubled inner peristomes. Interspace between the outer and inner peristomes wide, with a series of lamellar ribs on its outer surface. Shell slender conical; last whorl widest when removing the spiny ribs and expanded peristomes............................................................................. H. triplochilus sp. nov.

11b. Peristome double, with a single inner peristome. Interspace between the outer and inner peristomes almost smooth or with very low riblets on its outer surface. Shell frequently fusiform; penultimate whorl widest or last 2 whorls equally widest when removing the spiny ribs and expanded peristomes........................................................... 12

12a. Spiny projections of the axial ribs folded, widely opened toward the aperture. Upper margin of the axial ribs above the spiny projection (between the suture and the periphery) slightly protruded. Spiny ribs more closely spaced (15–20 ribs in a whorl)....................................................................... H. echinata echinata sp. et subsp. nov.

12b. Spiny projections of the axial ribs almost tubular. Upper margin of the axial ribs above the spiny projection (between the suture and the periphery) indistinct or very low. Spiny ribs widely spaced (10-13 ribs in a whorl)..................................................................................................... H. echinata tubulispina subsp. nov.

13a. Apical septum absent. Interspace between the wing-like ribs with a series of short and lamellar growth wrinkles above the suture of the last 1–2 whorls. Axial ribs above the aperture with developed or weakened wing-like projections. Aperture tilted downward against the coiling axis. Interspace between the outer and inner peristomes always narrow......................................................................................................... H. subalata sp. nov.

13b. Apical septum present. Interspace between the wing-like ribs without prominent axial sculpture above the suture. Axial ribs above the aperture without wing-like projections or with very low wing-like projections. Aperture hardly tilted against the coiling axis. Interspace between the outer and inner peristomes usually wider than 13a................................. 14

14a. Shell larger (shell height 6.7–8.3 mm). Interspace between the wing-like ribs with or without very low growth wrinkles below the suture on the penultimate whorl. Aperture strongly protruded. Inner peristome very widely expanded all around (particularly at the parietal side), thickened, strongly reflected backward. Parietal margin of inner peristome located near or expanded beyond the middle level of the upper body whorl. Outer peristome very widely expanded beyond the inner peristome. Interspace between the inner and outer peristomes usually wide......................... H. alata ( Crosse, 1866) comb. nov.

14b. Shell smaller (shell height 5.1–6.5 mm). Interspace between the wing-like ribs with a series of lamellar growth wrinkles below the suture on the penultimate whorl. Aperture hardly protruded. Inner peristome not so widely expanded nor thickened as 14a, hardly reflected. Parietal margin of inner peristome less expanded, frequently located below the middle level of the upper body whorl. Outer peristome not so wide as 14a. Interspace between the inner and outer peristomes rather narrow............................................................................................ H. pteriopurpuroides sp. nov.

Species description

Figures

FIGURE 1. Map of Palau islands showing collecting sites. Small red circles show collecting sites. Areas encircled by blue rectangles are shown as enlarged maps in Figs. 2–5. Abbreviations of the collecting sites are listed in Table 2.

FIGURE 7. Male soft parts of Palaina (Eupalaina) and Hungerfordia species. (A1, A2) P. (E.) patula Crosse, 1866, B0753; (B) P. (E.) sp.-20, live condition, B0732; (C) H. inflatula (Crosse, 1866), B0217; (D) H. pelewensis Beddome, 1889, live condition, B0651; (E) H. polymorpha (Crosse, 1866), live condition, B0659. Arrow heads indicate penes. Scale bars, 1mm. All specimens, UMUTZ-MG.

FIGURE 8. Radulae and buccal masses of Hungerfordia and Palaina (Eupalaina) species. (A1–A4) H. pelewensis Beddome, 1889, B0283; (B1–B4) H. polymorpha (Crosse, 1866), B0315; (C1–C4) P.(E.) sp.-20, B0595; (D1, D2) P.(E.) patula Crosse, 1866, B0320; (E1) H. pelewensis Beddome, 1889, buccal mass, B0283; (E2) H. polymorpha (Crosse, 1866), buccal mass, B0315; (E3) P. (E.) patula Crosse, 1866, buccal mass, B0320. Scale bars, 10 µm (A–D), 0.5 mm (E1–E3). All specimens, UMUTZ-MG.

FIGURE 10. Opercula of Palaina (Eupalaina) and Hungerfordia species. (A) P. (E.) moussoni Crosse, 1866, B0229; (B) P. (E.) dimorpha Crosse, 1866, B0087; (C) P. (E.) sp.-18, longitudinal section, B0082; (D) P. (E.) patula Crosse, 1866, B0204; (E) H. polymorpha (Crosse, 1866), B0049; (F) H. pelewensis Beddome, 1889, B0046; (G) H. polymorpha (Crosse, 1866), longitudinal section, B0049; (H) H. alata (Crosse, 1866), B0058. Oblique view of the outer surface, oblique view of the inner surface, and vertical view of the inner surface are shown from left to right in Figs. A, B, E, and F. Oblique view of the inner surface and vertical view of the inner surface are shown from left to right in Figs. D and H. Scale bars, 0.5 mm (A–B, D, E–F, H), 0.1 mm (C, G). All specimens, UMUTZ-MG.

FIGURE 11. Variation of shell shape and sculpture within and among Palaina (Eupalaina) and Hungerfordia species. (A) P. (E.) moussoni Crosse, 1866, shell height 2.8 mm, B0272; (B) P. (E.) sp.-15, shell height 2.6 mm, B0090; (C) P. (E.) strigata Crosse, 1866, shell height 4.2 mm, B0205; (D) P. (E.) patula Crosse, 1866, shell height 4.9 mm, B0204; (E) P. (E.) wilsoni Crosse, 1866, shell height 3.2 mm, B0296; (F) H. polymorpha (Crosse, 1866), shell height 3.8 mm, B0049; (G) H. sp.- 23, shell height 1.3 mm, B0149; (H) H. sp.-13, shell height 5.1 mm, B0250; (I) H. triplochilus sp. nov., shell height 5.9 mm, B0158; (J) H. alata (Crosse, 1866), shell height 7.4 mm, B0058; (K1, K2) H. goniobasis goniobasis sp. et subsp. nov., shell height 3.1 mm, B0092; (L1, L2) H. elegantissima sp. nov., shell height 3.4 mm, B0375; (M) H. pelewensis Beddome, 1889, shell height 3.1 mm, B0651; (N1, N2) H. pelewensis Beddome, 1889, shell height 3.1 mm, B0046. Arrow heads show positions of the constriction. All specimens, UMUTZ-MG.

FIGURES 2–3. Enlarged maps of Palau islands showing collecting sites. Top (Fig. 2), map of southern part of Babeldaob island; bottom (Fig. 3), map of Koror island and its neighboring islands or islets. Abbreviations of the collecting sites are listed in Table 2.