The taxonDrouetia Gude, 1911: 272. Gude, G.K., 1911. Note on some preoccupied molluscan generic names and proposed new genera of the family Zonitidae. Proceedings of the Malacological Society of London, 9: 269-27.
Diagnosis: “Shell hyaline, very finely striated and covered with
excessively fine spiral lines, non-umbilicated, with reflected, slightly twisted
columella.”
Riedel (1964) established the subgenus Atlantoxychilus for the closely related drouetian-type species:
Oxychilus (Drouetia) atlanticus (Morelet & Drouët, 1857)
Helix atlantica Morelet & Drouët, 1857: 149.
Diagnosis: Shell to about 10 mm, 6 whorls, spire somewhat raised. Vagina short. Proximal penis long, internally with weakly marked ridges if compared to those of the distal penis; epiphallic pore with weak, radiating ridges. Locus typicus: São Miguel, Açores. Remarks: Morelet & Drouët’s (1857) original description considered only one species throughout the archipelago; Riedel (1964) separated various subspecies, later raised to the specific level (Riedel, 1980, 1998), and restricted O. atlanticus to São Miguel. The type specimens at the Natural History Museum (London) are from Santa Maria and were ascribed to species other than O. atlanticus. Additional type specimens are deposited at the Muséum de Genève but their locality is marked “Açores”. On-going studies have revealed a complex of species in São Miguel; the identity of the true O. atlanticus is being ascertained by attempting to match specimens from the various “new” species with the shells of the Genève types, on the assumption that they are from São Miguel. Taking into consideration a series of studies on specimens from Mosteiros and Abelheira, referred to O. atlanticus, the pattern therein observed is being provisionally treated as that of O. atlanticus.
Oxychilus (Drouetia) minor (Morelet, 1860)
Helix atlantica, var β minor Morelet, 1860: 168.
Diagnosis: Shell small (6 mm, 5 whorls). Animal pink. Locus typicus: Fayal, Açores. Remarks: Raised to subspecific status by Riedel (1964), it is restricted to Fayal. The extent to which it could live also on Pico or any other island of the Central Group is under investigation (see Martins et al., 2006).
Oxychilus (Drouetia) brincki Riedel, 1964
Oxychilus atlanticus brincki Riedel, 1964: 31.
Diagnosis: Shell large (10 mm, 6,5 whorls). Animal with dark blue neck and orange foot. Penis massive; epiphallus entering subapically; many internal ridges radiating from epiphallic pore and descending over distal penis. Locus typicus: Santa Maria, Açores. Remarks: Originally recognized as a subspecies of O. atlanticus by Riedel (1964), it was later raised to specific status. Restricted to Santa Maria (see Martins, 2005).
Oxychilus (Drouetia) agostinhoi Martins, 1981
Oxychilus (Drouetia) agostinhoi Martins, 1981: 248.
Diagnosis: Shell small (5 mm, 4 whorls), spire very flat, last whorl expanding. Mesocone of central tooth of same length as ectocones. Locus typicus: Fontinhas (Pico Alto), Santa Maria, Açores. Remarks: The smallest species of this subgenus. Restricted to Pico Alto. Rare. Due to its narrow distribution, it should be considered endangered.
Oxychilus (Drouetia) miceui Martins, 1989
Oxychilus (Drouetia) miceui Martins, 1989: 57.
Diagnosis: Shell 7,5 mm, 5,7 whorls, spire flat, last whorl of quadrangular profile. Proximal penis thin, penial sheath short. Locus typicus: Caldeira de Santa Bárbara, Terceira, Açores. Remarks: O. miceui lives mostly on mountains with endemic vegetation, and does not overlap with the following species.
Oxychilus (Drouetia) furtadoi Martins, 1989
Oxychilus (Drouetia) furtadoi Martins, 1989: 61.
Diagnosis: Shell 6,7 mm, 5,6 whorls, spire flat, last whorl of rounded profile. Proximal penis thick, penial sheath long. Locus typicus: Fonte da Telha, Posto Santo, Terceira, Açores. Remarks: O. furtadoi lives mostly on areas of secondary vegetation. It resembles some forms of the highly diversified O. atlanticus and additional studies are in progress to confirm its specific status.
Oxychilus (Drouetia) batalhana de Winter, 1989
Oxychilus (Drouetia) batalhana de Winter, 1989
Diagnosis: Shell 8,4 mm, 6 whorls, spire flat, last whorl of rounded, spire relatively high. Proximal penis thin, long. Locus typicus: Batalha, São Miguel, Açores. Remarks: O. batalhana appears to be a mere form of the highly variable O. atlanticus and additional studies are in progress to confirm its specific status.
Oxychilus (Atlantoxychilus) riedeli Hausdorf, 1993
Helix atlantica, var γ spectabilis Morelet, 1860: 168
(= Oxychilus riedeli Hausdorf, 1993).
Diagnosis: Shell small (5 mm), with a furrow on shoulder of whorls. Penis internally with pilasters and papillae, and a distinct stimulator-type organ. Locus typicus: Santa Maria, Açores. Remarks: Raised to specific status by Riedel (1964), for which a new subgenus was created. Since the original name was pre-occupied by Helix spectabilis Pfeiffer, 1844, Hausdorf (1993) introduced the present specific name, dedicated to Adolf Riedel. Restricted to Santa Maria (see Martins, 2005).
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