Arinia ( Notharinia ) boucheti Páll-Gergely, 2018

Arinia ( Notharinia) boucheti Páll-Gergely View in CoL , n. sp.

( Fig. 2 View FIG )

TYPE MATERIAL. — Northern Laos. Phuom Laong, coll. Saurin, MNHN-IM- 2014-6415 ( holotype, H = 1.88 mm, D = 0.81 mm); same data, MNHN-IM- 2014-6416 ( 2 paratypes) .

ETYMOLOGY. — This species is dedicated to and named after Prof. Philippe Bouchet to acknowledge that he tracked Edmond Saurin’s ( 1904-1977) material in the late 1970’s, and made it available for study.

TYPE LOCALITY. — Northern Laos, Phuom Laong.

DIAGNOSIS. — A Notharinia species with strong, comparatively widely-spaced ribs, oblique aperture, and clearly separated inner and outer peristomes.

DIFFERENTIAL DIAGNOSIS. — The most similar species in terms of shell size, shape, and rib density is Arinia ( Notharinia) crassilabris Vermeulen, Phung & Truong, 2007 . That species, however, differs from the new species in the following traits: aperture is less oblique to the shell axis; the boundary between the two peristomes is hardly visible; and the outer peristome is less reflected.

DISTRIBUTION. — This species is known from the type locality only.

DESCRIPTION

Shell whitish, semitransparent, cylindrical, typical to Notharinia ; constriction not observed; protoconch oblique, with 1-1.25 whorls, nearly smooth, extremely finely pitted; apex sunken; teleoconch rather regularly, strongly ribbed, rib density decreasing towards aperture; no spiral striation observed on entire shell; whorls 4.75-5.5; aperture rounded, strongly oblique to shell axis; peristome adnate to penultimate whorl; inner peristome protruding, outer peristome expanded but not reflected; boundary between two peristomes conspicuous; individual ribs elevated, slightly bent anteriorly; umbilicus closed. Operculum and soft anatomy unknown.

Measurements (in mm)

H = 1.57-1.88, D = 0.81 (n = 2).

REMARKS

Currently five species of the subgenus Notharinia are known: Arinia ( Notharinia) attenuata ( Vermeulen, Phung & Truong, 2007) , A. ( N.) brevior ( Vermeulen, Phung & Truong, 2007) , A. ( N.) crassilabris , A. ( N.) linnei ( Maassen, 2008) , and A. ( N.) micro Marzuki & Foon, 2016 . The former three species were described from Southern Vietnam’s Kien Giang Province, whereas the latter two species are known from the Malay Peninsula. Two further undescribed species ( Notharinia sp. nov. ‘Khoe La’ and Notharinia sp. nov. ‘Khoe La & Ong’), also from Kien Giang Province, were assessed using to IUCN criteria ( Vermeulen & Anker 2016a, b). The type locality of Arinia ( Notharinia) boucheti Páll-Gergely , n. sp. could not be located on the map, but it must be somewhere in Northern Laos. The occurrence of a Notharinia species in northern Laos considerably extends the distribution of the subgenus northwards.

There is an unusually large variation in terms of the number of whorls in Arinia ( Notharinia) boucheti Páll-Gergely , n. sp. Similar observations were made by Marzuki & Foon (2016) in A. ( N.) micro . We might assume that the high variability of whorl numbers is characteristic for this subgenus.