Helicina rhodostoma

Robert John Lechmere Guppy (1868)^[5] noted that this species is not found above 1000 m altitude.^[2] Three names have been used for this species, but material by Robinson et al. (2009)^[2] shows that the forms intergrade, illustrating the variability of the species. In general, populations from higher altitudes have a more pronounced columellar spine, and are more likely to have a red to reddish-orange aperture, as seen in typical Helicina rhodostoma.^[2] Populations from drier, coastal areas tend to lack a columellar spine, and the aperture may be white or yellow.^[2] Juvenile specimens of this species often have a hairy periostracum, which is gradually worn off as the snail reaches sexual maturity.^[2]

Helicina rhodostoma is endemic to the West Indian island of Dominica.^[2]

Despite the fact that Helicina rhodostoma was originally erroneously described from Guadeloupe – and in subsequent reports from that island the error has been perpetuated – this species is undoubtedly a Dominican endemic.^[2] It has not been found during subsequent surveys of Guadeloupe and Marie-Galante.^[2] The fact that no museum material exists labelled “Guadeloupe”, not even in the Muséum national d'histoire naturelle in Paris, indicates that the species has never been collected on that island.^[2] The synonymy of Helicina goldfussi and Helicina rhodostoma inermis is confirmed by morphometrics and anatomical studies.^[2]