Excerpts from Jim Conrad's
Naturalist Newsletter

cf. Longspine Starsnail, ASTRALIUM PHOEBIUM

from the September 4, 2011 Newsletter issued from Mayan Beach Garden Inn 20 kms north of Mahahual; Caribbean coastal beach and mangroves, ~N18.89°, ~W87.64°, Quintana Roo state, MÉXICO
STARSNAIL
Having such poor vision, I concentrate so hard on not tripping over things that often I overlook what's right beside the path. That's when it's good to have along a kid like the one the other day on a Nature walk. What a wonder that he noticed so many things and wanted to know about them. He found the little shell shown above.

That's basically a snail shell with sharp dentations along the coil crests, so we know right off that we have gastropod (snails and slugs), which is a kind of mollusk; it's not something like a clam or barnacle shell.

However, the experts' say that maybe around 85,000 kinds of gastropods exist, so calling something a gastropod isn't saying much. Volunteer identifier Bea in Ontario steered me to the Turban Snail Family, the Turbinidae, but at that point it becomes harder to get a solid name for it.

A good guess is that we have the Longspine Starsnail, ASTRALIUM PHOEBIUM. Most pictures of that species show its shell bearing longer, sharper spines, but shells worn by waves look like ours. The main reason for guessing that it's Astralium phoebium is that that species is known to be common in our part of the world, from the North Carolina coast south through the Gulf of Mexico to Venezuela.

Longspine Starsnails have been recorded from shallow water to depths up to 137 meters (450ft). They graze on microalgae and diatoms. A website specializing in aquarium pets tells us that starsnails in general occupy rocky, rubble-covered environments. If they fall onto their backs onto flat, open sand they're unable to right themselves. They should be kept in aquaria with rocky, irregular bottoms.