AMPLIRHAGADA AMBULATOR SP. NOV.

FIGURES 7D–H, 10, 11

Amplirhagada alta intermedia – Solem, 1981: 270– 271, fig. 59e (partim).

Type locality: Western Australia, Kimberley, Bonaparte Archipelago, East Montalivet Island (14°17′17.8″S, 125°17′40.1″E) .

Material examined: Holotype WAM S42936 (dissected specimen) . Paratypes WAM S33011 (three preserved specimens), WAM S33019 (three preserved specimens), AM C.470981 (preserved body). Additional non-type material: WAM S33012, WAM S33018, WAM S33020, WAM S33023, WAM S33025 -7, WAM S42932 -5, AM C.470982-4 (Table 1).

Etymology: For ‘ambulator’ (Latin: a walker, one who walks about), in reference to J. J. Walker, who collected specimens that facilitated the pioneer study of E. A. Smith (1894); noun in apposition.

Description: Shell (Fig. 7D–H) variable in shape and colour; broadly conical to nearly beehive-shaped, with moderately to highly elevated spire; periphery rounded to slightly compressed (Table 3). Teleoconch smooth with regular, faint axial growth lines only. Umbilicus 50–100% concealed by columellar reflection. Background colour and base crème, with welldeveloped brown sub-sutural and mid-whorl bands, in about one-third of specimens bands blending into each other, covering upper part of shell in uniform, dark brown tone; lip colour white (Table 4). Aperture simple, slightly to well expanded, slightly reflected, with weak or wanting basal node. Genital anatomy (Figs 10, 11). Penis tubular, very long, coiled; vas deferens entering penial sheath in posterior third, penial retractor muscle moderate in length; penial verge short (~ 1/10 length of penial chamber); inner penial wall with short, corrugated main pilaster in posterior part, segments supporting row of little hooks; several indistinct, narrow longitudinal pilasters form on posterior portion tapering in prominence towards posterior end, one more strongly developed undulating pilaster comprising posterior half of penial wall; densely packed, small pustules on posterior part of penial wall only along with one longitudinal pilaster. Vagina long (but shorter than penis), tubular; bursa copulatrix long, extending to anterior end of spermoviduct, with inflated head.

Comparative remarks: Shell differing from A. fitzpatricki from West Montalivet Island most conspicuously by absence of fine, regular axial ribs on upper whorls, and larger size, and from A. montalivetensis by more elevated shape and larger number of whorls (Table 3). Genital and penial anatomy of all three species is similar in general (conspicuously elongated bursa copulatrix, penis). However, A. ambulator is characterized by absence of penial wall pustules on posterior portion (present in A. montalivetensis), very short main stimulatory pilaster restricted to proximal part of inner penial wall (extending further anteriorly in A. montalivetensis, A. fitzpatricki), presence of undulating longitudinal pilasters (absent in other species), one single anterior pilaster (many in other species). This species was mistaken for A. intermedia from South Maret Island by Solem (1981).

Distribution: East Montalivet Island group, including Don, Patricia, and Un-named Island (Fig. 6).