Ledella favus Hoffman & Little, 2025

Ledella favus Hoffman & Little sp. nov.

Fig. 13B–D View Fig .

Zoobank LCID: urn:lsid:zoobank.org:act:C0663527-E813-4D74-B94B B85AAE34D9F6.

Etymology: After the honeycomb ( favus in Latin) sculpture on the prodissoconch.

Type material: Holotype, one shell, SMF373069 About SMF . Paratypes, one valve, SMF373071 About SMF ; one shell, SMF373070 About SMF , from the type locality and horizon .

Type locality: Northern Indian Ocean, Krishna-Godavari Basin , Bay of Bengal, offshore eastern India, 15°51.6335’ N, 81°50.2274’ E, 1046 m water depth GoogleMaps .

Type horizon: 16.28–16.88 mbsf level, core NGHP-01-12A; Upper Pleistocene .

Material.— Type material and several specimens from core

NGHP-01-12A (for details see Table 1).

Diagnosis.—Solid shell, oval outline, posteriorly truncated obliquely: strong co-marginal growth margins; length up to 6 mm. Internally smooth, broad hinge plates and heavy dentation.

Dimensions.— Holotype height 4.2 mm, length 5.8 mm, tumidity 3.2 mm. Maximum dimensions of shells in type set as in holotype.

Description.—Prodissoconch single stage evident only, oblong, truncated dorsally, flattened, raised ridge on dorsal side with pointed end; sculpture with central hexagonal network (honeycomb-like), smooth at margins. Transition to dissoconch clear by change in sculpture. Length 200 μm. Dissoconch with straightened dorsal outline posteriorly; ventral and anterior margins convex; posterior with obliquely truncated cusp at end of ridge; shell moderately inflated. Lunule and escutcheon long and lanceolate, escutcheon somewhat inconspicuous, both with fine growth lines. Margins sharp and smooth. Sculpture with regular co-marginal growth stages, width growth lines equal to inter-spaces. Internal surface and margin smooth; muscle scars and pallial line inconspicuous. Pallial line without sinus. Hinge only known from right valve; wide hinge plates at 120°; nine sharp teeth on either side (in right valve with length 4 mm), rectangular in cross-section, central teeth in either row most pronounced. Triangular resilifer placed centrally below umbo.

Remarks.—Placement in Ledella is based on the truncatedoval outline with a cusp, the solid shell, the wide hinge plates each with few teeth and the clear resilifer. The bathyal Ledella procumbens ( Prashad, 1932) is known from the Bay of Bengal in 450–1820 m ( Huber 2010). This species has a long pointed rostrum, unlike our specimens ( Prashad 1932: 20, pl. 1: 21–22). The cosmopolitan type species Ledella ultima ( Smith, 1885) has a more globose shell, convex dorsal outline posteriorly, and has thickened (box-shaped) margins when adult ( Knudsen 1970). Tan (2021) reported a similarly shaped species, Nuculana cf. corbuloides ( Smith, 1885) , from deep water off Java but this species has a more pointed rostrum and coarser co-marginal ribs. The prodissoconch sculpture on Ledella favus Hoffman & Little sp. nov. resembles that of other modern and fossil nuculanids, for example Nuculana grasslei Allen, 1993 ( Allen 1993: figs. 2, 3; Kiel 2006).

Stratigraphic and geographic range.— Type locality and horizon only.