Kleokyphus hypsus Solem, 1976

Figures 20A–C; 21; 35L; 37D; 39.

Libera gregaria Garrett—Aubert de la Rüe & Soyer 1958, p. 365, non Libera gregaria Garrett 1884. Kleokyphus hypsus Solem 1976, pp. 226–227, table 75, figs 95d–f.

Examined material (327 specimens). Holotype: MNHN 25571. Tuamotu Islands: Makatea. Collected by E. Aubert de la Rüe in 1955. Additional material: 1 shell, Mk12; MNHN 25572, 325 shells, Mk19.

Type locality. Tuamotu Islands: Makatea.

Diagnosis. Shell less than 7 mm in diameter, robust, subdepressed, flammulated; teleoconch sculptured by very low, relatively crowded primary axial ribs (> 100 ribs on body whorl); umbilicus U-shaped; palatal wall usually with 5, rarely with 4 or 6 barriers, rarely accompanied by 1 trace; parietal wall with 3 barriers, rarely accompanied by up to 3 traces.

Description. Shell subdepressed, white, with regularly spaced, amber flammulations, usually stronger apically than on body whorl, fading out on the shell base. Shell wall robust, opaque; periostracum adherent, matt. Apex barely elevated, spire moderately raised; whorls descending progressively more rapidly. Whorls and periphery rounded. Apical and umbilical sutures impressed. Transition between protoconch and teleoconch indistinct. Sculpture of the first whorl unknown; second whorl onwards ornamented by a primary sculpture of very low axial ribs, with interspaces 2–4 times their width and by a secondary sculpture of fine, crowded axial riblets, with interspaces c. 1–2 times their width; secondary riblets occupying the interspaces between each pair of primary ribs. Spiral cording present from the fourth whorl onwards, overlaying the axial sculpture. Umbilicus very deep, Ushaped, slightly narrower apically than at last whorl. Peristome crescent-shaped; columellar lip slightly reflected. Palatal barriers usually 5, rarely 4 or 6, slightly recessed within aperture, approximately equidistant; barrier 1 columellar in position, extending beyond the line of vision from the aperture, usually similar to barrier 5 in prominence, occasionally represented by a trace, rarely absent; barriers 2 to 5 extending c. 1/8 whorl, descending gradually posteriorly; barrier 2 usually descending more abruptly anteriorly than barriers 3 to 5; barriers 2 to 4 similar in prominence, taller and wider than barriers 1 and 5; barrier 3 rarely duplicated, increasing the number of palatals to 6. Palatal trace rarely present, positioned near the apical suture. Parietal wall with 3 barriers and, rarely, up to 3 traces; barriers similar in prominence, approximately equidistant, extending slightly less than 3/16 whorl; trace 1, when present, positioned near the apical suture or between barriers 2 and 3; traces 2 and 3, when present, positioned between barrier 3 and umbilical suture. Other shell features that can be expressed numerically are shown in Table 2.

Remarks. K. hypsus was previously known only from the severely worn holotype (Fig. 20A). Specimens recovered from station Mk19 reveal the coloration pattern of the species (Fig. 20B–C), details of its sculpture and intraspecific variation in the number and arrangement of the apertural barriers (Fig. 21). Fully grown specimens of K. hypsus are easily separated from other representatives of the genus by the very large size and robust build of their shells. A comparatively high aperture (width approximately equal to the height) is the best criterion for identifying specimens with 5 or fewer whorls (Fig. 20C).