Seguenzioidea Verrill, 1884

Superfamily Seguenzioidea Verrill, 1884 View in CoL Seguenzioidea gen. et sp. indet.

Fig. 7 View Fig .

Material.— Two shells, SMF373111 About SMF and one lost in processing. Northern Indian Ocean, Krishna-Godavari Basin , Bay of Bengal, offshore eastern India, 15°51.6335’ N, 81°50.2274’ E, 1046 m water depth, 16.18–16.38 mbsf level, core NGHP-01- 12A; Upper Pleistocene GoogleMaps .

Description.—Small shell with broad spire, umbilicate. Protoconch paucispiral, three quarters whorl, small nucleus, sculpture with weak tiny dimples, terminal smooth straight rim, diameter about 300 µm. Teleoconch with two convex whorls with slightly cyrtoconoid outline, sculpture with numerous flexuous growth lines, suture deep, umbilicus filled but probably wide and deep. Aperture broad piriform, outer lip thin, prosocline, columellar lip sharp.

Remarks.—Specific characters are the flexuous growth lines and prosocline lip. The general outline and protoconch are clearly skeneimorph, but the small number of collected specimens precludes us identifying them at a lower taxonomic level. The shells are very similar to Akritogyra curvilineata Warén, 1992 , from the NE Atlantic. This genus has not yet been assigned to a family in the Seguenzioidea .

Family Skeneidae Clark, 1851 View in CoL

Genus Cirsonella Angas, 1877 View in CoL

Type species: Cirsonella australis Angas, 1877 , junior synonym of Cirsonella weldii ( Tenison Woods, 1877) , by monotypy; Recent, New South Wales, Australia.

Cirsonella aperta Hoffman & Little sp. nov. Fig. 8 View Fig .

Zoobank LCID: LSIDurn:lsid:zoobank.org:act: 60068CBB-196B-4C4E-82E5-8F4CD3D84E52.

Etymology: With reference to the partly open umbilicus.

Type material: Holotype, shell, SMF373123 About SMF . Paratypes, one shell, SMF 373118 About SMF ; one shell, SMF373119 About SMF ; one shell, SMF373120 About SMF ; one shell, SMF373121 About SMF ; two shells, SMF373122 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: 16.18–16.88 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.—Small shell with moderately raised spire, solid, smooth, narrow open umbilicus, umbilical chink with two broad spiral cords, suture shallow impressed.

Dimensions.— Holotype height 1.7 mm, length 2.0 mm. Shells in type set maximum height 2.1 mm, length 2.3 mm.

Description.—Protoconch single stage only, half whorl, flattened, smooth, curved sharp lip. Transition to dissoconch clear by labial margin. Length 330 µm. Teleoconch raised with flat apex, two convex whorls. Smooth, slightly flexuous growth lines. Umbilical area demarcated with rim, few axial, curved ridges with variable strength fill area to columella, narrow open umbilical slit. Aperture subcircular, internally smooth with (operculum?) edge near external margin, external lip blunt.

Remarks.—We place the species in Cirsonella ( Skeneidae ) on the basis of the morphology of the protoconch, teleoconch and the partly closed umbilicus. Alternatively, it could be placed in the genus Skenea Fleming, 1825 . Species in Cirsonella are widely distributed, e.g., the Northern Atlantic, the SW Pacific (off Australia and New Zealand), South Africa and the Kerguelen Islands (MolluscaBase 2024). This is the first species from the Northern Indian Ocean. An open umbilicus is typical in young specimens and a narrow umbilical slit is common in for example the NE Atlantic Cirsonella ateles ( Dautzenberg & Fischer, 1896) and Cirsonella gaudryi Dautzenberg & Fischer, 1896 ) ( Hoffman et al. 2020: 55–59, figs. 48–49). Known species show a well-defined chink in the umbilical area; the open umbilicus is often covered by smooth columellar callus in adult specimens. The umbilical grooves and ridges distinguish Cirsonella aperta Hoffman & Little sp. nov. from other described species.

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