Hungerfordia ngereamensis M. Yamazaki and Ueshima

Yamazaki, Midori, Yamazaki, Kazunori, Rundell, J. & Ueshima, Rei, 2015, Systematic review of diplommatinid land snails (Caenogastropoda, Diplommatinidae) endemic to the Palau Islands. (3) Description of eight new species and two new subspecies of Hungerfordia, Zootaxa 4057 (4), pp. 511-538 : 514-516

Hungerfordia ngereamensis M. Yamazaki and Ueshima sp. nov.

(Figs. 2, 12 O)

Material examined. Holotype. Chongelungel, south of Ngeream (Loc. BA4-2), Airai state, Babeldaob island, Palau. Collected by R. U. and M. Y. on July 7, 2006. UMUTZ-MG-B0293T. Paratypes. Babeldaob: Loc. BA3-1, 10 specimens, 27/VI/2005, UMUTZ-MG-B0172; Loc. BA4-2, 26 specimens, 7/VII/2006, UMUTZ-MG-B0293.

Diagnosis. Shell sinistral, large to medium-size for Hungerfordia species, slender conical. Shell color white, upper whorls frequently yellow or yellowish brown. Apical septum absent. Axial rib on most whorls highly protruded as spines, very widely spaced, strongly folded at the peripheries of the whorls; spiny projections of the ribs moderately high, rather narrow, arising at some distance below the suture; ribs above the aperture abruptly becoming closely spaced, with greatly reduced spiny projections, less folded. Interspace between the spiny ribs with some very weak and very short growth wrinkles below the suture on the lower whorls. Spiral sculptures present throughout teleoconch. Aperture weakly protruded. Columellar tooth very weakly emerged within the aperture in front view, but strongly developed deeply inward. Peristome triple, with doubled inner peristomes, stout. Outer peristome strongly developed, widely expanded. Inner peristome double, also expanded; distal inner peristome strongly developed just behind the proximal inner peristome, gradually narrowed toward the aperture; proximal inner peristome always narrower than the distal one in front view. Interspace between the outer and inner peristomes wide; outer surface with a series of fine and very low riblets at the abapertural half (near the outer peristome), almost smooth on the adapertural half (just behind the inner peristomes).

Description. Shell (Figs. 2A–F, 12 O). Shell sinistral, large to medium-size for Hungerfordia species, conical or fusiform, penultimate whorl widest (slightly wider than the last whorl) or last 2 whorls almost equally widest when removing the expanded ribs and peristomes; sides almost straight. Shell color white, upper whorls occasionally yellow. Whorls 6–7, slightly convex; last 1/8 whorls (including the interspace between the outer and inner peristomes) expanded upward and ascending onto the penultimate whorl in left lateral view. Suture weakly impressed. Constriction located above the parietal/columellar junction of the inner peristome, associated with abrupt changes of the ribbing pattern, internally without palatal plica except a low axial-crest caused by the constriction. Tuba 7/8 whorls. Protoconch 1+1/8–1+1/4 whorls, almost smooth, very weakly and finely punctated. Apical septum absent. Axial ribs strongly developed on the teleoconch, oblique to the coiling axis, highly protruded as spines on most whorls: ribs on the first 1/3–1/2 whorls of the initial teleoconch weak, almost straight (not folded at the peripheries of the whorls), initially closely spaced and very low, gradually becoming widely spaced and stronger; ribs on the subsequent whorls except above the aperture (ribs on most whorls except above the aperture) strong, highly protruded as spines, very widely spaced (9–11 ribs in a whorl), not synchronized with those on the previous whorls, strongly folded at the peripheries of the whorls, strongly elevated by axial protrusions of shell wall (along the ribs) on the last 3/4 whorls; upper margin of the ribs above the spiny projections (between the suture and spines) very low, never protruded, indistinct; spiny projections of the ribs high, pointed, folded at the peripheries of the whorls, trough-shaped, rather narrow, arising at some distance below the suture (arising near the peripheries of the whorls), upper margin folded over the lower margin, lower margin gradually decreased in height and extended below to the suture of the next whorl, with fine spiral sculptures on the outer surface, protruded upward on most whorls, becoming protruded laterally on the last 5/8 whorls; ribs above the aperture (ribs on the last 1 to last 3/4 whorls around the constriction) abruptly becoming low and closely spaced, with greatly reduced spiny projections (but still retaining very low spiny projections), less folded than those on the preceding whorl, becoming much less folded toward the aperture, partially hidden by the inner peristome. Interspace between the spiny ribs smooth on the upper whorls, with some growth wrinkles below the suture on the last 1.25–2.25 whorls; growth wrinkles developed below the suture on the lower whorls, closely spaced, short, very low, initially very weak, becoming rather prominent on the last 3/4 whorls. Spiral sculptures present throughout the teleoconch, fine, rather prominent, sinuous in high magnification, extending on the outer surface of the spiny ribs and outer peristome. Base rather convex, without basal fold; interspace between the ribs with a series of fine and short growth wrinkles around the columella. Axial protrusions of shell wall (along the ribs) on the last 3/4 whorls strongly developed, hidden by the spiny ribs in fresh specimens (becoming obvious after removal of the spiny projections of the ribs), associated with prominent axial depressions between them; abapertural side slightly or hardly convex in umbilical view; adapertural side well convex, wider than the abapertural side in umbilical view. Umbilicus closed in adult. Aperture hardly or slightly tilted against the coiling axis (in left lateral view), slightly protruded from the previous whorl; columellar axis within the aperture almost vertical or slightly oblique in front view. Columellar tooth present, very weakly appearing within the aperture in front view, but strongly developed deeply inside the aperture, never extended onto the inner peristome. Peristome triple, with an outer peristome and doubled inner peristomes. Outer peristome strongly developed, widely expanded, but hardly or only slightly expanded beyond the inner peristome in front view, obtusely angulate at the palatal side, frequently with a rounded baso-columellar edge, reflected backward, abruptly expanded from the preceding whorl, with concentric growth riblets or growth lines on the inner surface, with fine spiral sculptures on the outer surface. Inner peristome strongly protruded (separated) from the outer one, double with distal and proximal inner peristomes; distal inner peristome strongly developed just behind the proximal one, widely expanded, shortly expanded beyond the proximal one in front view; proximal inner peristome squarish circular, always narrower and weaker than the distal one, rather widely expanded, parietal margin almost straight and located near or below the middle level of the upper body whorl. Interspace between the outer and inner peristomes wide, with a series of fine riblets on the outer surface near the outer peristome, rather smooth near the inner peristome; uppermost margin (= suture) ascending onto the penultimate whorl toward the aperture in left lateral view; base extended almost horizontally in left lateral view.

Dimensions. Shell height 4.5–5.3 mm, diameter 2.6–3.6 mm, suture width 1.9–2.1 mm, aperture height 1.8– 2.2 mm.

Operculum (Figs. 2G1–4). Operculum corneous, multispiral, circular, transparent, amber colored, thin, flat; outer surface smooth; inner surface with a very weak arcuate ridge near the columellar margin.

Penis. Penis absent.

Radula . Not examined.

Distribution and ecology. Endemic to Palau: Southern limestone coast of Babeldaob island. This species inhabits limestone rocks.

Remarks. H. ngereamensis is most similar to H. triplochilus Yamazaki & Ueshima, 2013 (Figs. 12 O, P), but differs in the following points: the axial protrusions of shell wall along the ribs are strongly developed on the last 3/ 4 whorls; the riblets between the inner and outer peristomes are less developed, much lower than the latter species; the distal inner peristome is always wider and more strongly developed than the proximal inner peristome; the shell is broader and less slender; the distribution is endemic to Babeldaob island.

H. ngereamensis differs from a sympatric congener, H. echinata tubulispina Yamazaki & Ueshima, 2013 , in the following points: the spiny projections of the ribs are wider, never tubular; the inner peristome is double; the interspace between the outer and inner peristomes is wider; the axial ribs above the aperture have very short spiny projections. H. ngereamensis also differs from H. expansilabris Yamazaki & Ueshima, 2013 , which is distributed in the same area of Babeldaob island, in the following points: the outer and inner peristomes are not so widely expanded as the latter species, more robust; the columellar tooth is present; the distal inner peristome is always wider and more strongly developed than the proximal inner peristome; the axial ribs above the aperture have short spiny projections.

Etymology. The specific name is derived from the type locality.

FIGURE 2. Hungerfordia ngereamensis sp. nov. (A1–6) A topotypic paratype, Loc. BA4-2, B0293a; (B1–2) a topotypic paratype after removal of the spiny projections of the axial ribs, B0293b: (B1) umbilical view, only the last whorl shown, note that the axial protrusions of the shell wall are strongly developed along the ribs; (B2) oblique dorsal view, showing the axial protrusions of the shell wall on the last 3/4 whorls; (C1–2) a yellowish and subfusiform specimen, a topotypic paratype, B0293c: (C2) sculptures on the upper body whorl, showing the reduced axial ribs above the aperture; (D) columellar tooth, dorsal view of a partially opened shell, a topotypic paratype, B0293d; (E1–6) holotype, B0293T; (F) a worn specimen, only the last whorl shown, note the axial protrusions of the shell wall which are usually hidden by spiny ribs in fresh specimens (see Fig. E6), a topotypic paratype, B0293e; (G1–2) outer surface, and (G3–4) inner surface of operculum, a topotypic paratype, B0293. Scale bars, 1mm (A–F), 0.5 mm (G). All specimens, UMUTZ-MG.