The shell is smooth, shining, not striate spirally, generally somewhat more depressed, deep chestnut or reddish brown. Whorls are a little flattened near the suture.[1] The species may have subtle spiral striation, although there exists considerable variation; axial growth lines are clearly visible.[2]
The operculum is horny, diaphanous, concave externally, cartilaginous within, the nucleus projecting internally; with from ten to fourteen very narrow whorls, their rather lamellar outer edges slightly free.[1]
Amphicyclotulus amethystinus has spiral threads absent or only weakly present.[2] There are found only two species in the genus Amphicyclotulus in Dominica. The other species is Amphicyclotulus dominicensis and it has spiral cords clearly present and raised.[2]
Apical view of the shell. Width of the shell is 14.1 mm.
Apical view of the shell. Width of the shell is 18.4 mm.
Robert John Lechmere Guppy (1868)[1] noted that this species is not found above 1000 m. Although he recognized two "forms", he did not recognize two separate species. George French Angas (1884)[4] subsequently recorded "Cyclophorus amethystinus" from altitudes above 1200 m. Paul Bartsch (1942)[5] restricted the name amesthystinus to Guppy’s var. β, the "smooth, shining, not striate spirally" form.[2]
Distribution
Distribution of Amphicyclotulus amethystinus (green dots) and Amphicyclotulus dominicensis (one blue dot) in Dominica.
↑ Angas G. F. (1884). "On the terrestrial Mollusca of Dominica, collected during a recent visit to that island". Proceedings of the Zoological Society of London1883: 594-597, figs 1-3.
↑ Bartsch P. (1942). "The cyclophorid mollusks of the West Indies, exclusive of Cuba": 43-141. In: Torre C. de la, Bartsch P. & Morrison J. P. E. (1942). The cyclophorid operculate land mollusks of America. Bulletin United States National Museum181: 1-306, pls 1-42.
