Volvulella fortis (Thiele, 1925)

Valdés, Ángel, 2008, Deep-sea “ cephalaspidean ” heterobranchs (Gastropoda) from the tropical southwest Pacific, Mémoires du Muséum national d'Histoire naturelle 196, pp. 587-792 : 751

publication ID	978-2-85653-614-8
DOI	https://doi.org/10.5281/zenodo.5491871
persistent identifier	https://treatment.plazi.org/id/03D087B2-FF40-BE8A-FF01-74E8F666F989
treatment provided by	Felipe
scientific name	Volvulella fortis (Thiele, 1925)
status

Treatment

Volvulella fortis (Thiele, 1925) View in CoL

Figs 81C, 82

Volvula fortis Thiele, 1925: 239 , pl. 31, fig. 23.

TYPE MATERIAL . — Probably lost (could not be located at ZMA).

TYPE LOCALITY. — Nias south Channel, Indonesia, 0°30.2’N, 97°59.7’E, 132 m [ Valdivia : stn 193] GoogleMaps .

MATERIAL EXAMINED. — New Caledonia proper. BATHUS 1 : stn DW 654 , Passe de Canala , 21°17’S, 165°57’E, 237-298 m, 2 dd (Fig. 81C); stn DW674 , Grande Passe de Touho, 20°49’S, 165°19’E, 105-110 m, 1 dd GoogleMaps .

DISTRIBUTION. — Originally described from the south of Nias Island, off Sumatra, Indonesia, in 123 m (Thiele, 1925). The material herein represents the first record from New Caledonia (Fig. 82), in 110-237 m.

DESCRIPTION. — Shell morphology. Length 2.5 mm, width 0.8 mm (largest specimen examined). Shell fragile, elongate, with nearly parallel sides (Fig. 81C). Only 1 whorl visible, forming the entire shell. Anterior end of the shell rounded. Umbilicus closed. Aperture long, wide anteriorly, narrowing gradually at about 1/3-1/2 of its length. At its apical end, the aperture bends over the apex of the shell and the parietal wall forms a short spine that completely covers the apex. Columellar margin slightly twisted anteriorly. Sculpture of 13 simple spiral grooves at the posterior end and 6 at the anterior end. Colour uniformly whitish.

Anatomy. Unknown. All shells collected lacked soft parts.

REMARKS. — Volvulella fortis was originally described as an elongate species with spiral grooves near the two ends of the shell. The material from New Caledonia examined here matches the original description. Volvulella ovulina has a much shorter and wider shell and the spiral grooves are only present near the anterior end of the shell.

Two other similar species are Volvulella radiola (A. Adams, 1862) and Volvulella tokunagai (Makiyama, 1927) , which also have an elongate shell, but they both have the entire surface of the shell covered with widely separated faint spiral grooves.