Agathistoma excavatum reaches 18 mm (approximately 0.7 inch). The typical trochiform shape is complemented by a concave (“excavated”, hence the species-name ending) base, which sometimes can show a greenish color. The species is found in the Caribbean, Gulf of Mexico, and the Florida Keys. The shell illustrated was found on Captiva Island on a stormy day in October 2021 by Lisa Johnstone. Its presence on the local beaches had not been registered before, and this first record for Captiva should, as usual in cases like this, be considered with caution.
