Excerpts from Jim Conrad's
from the March 29, 2015 Newsletter issued from Río Lagartos, on the north-central coast of Yucatán, MÉXICO
ATLANTIC BUBBLE SHELL
Across the estuary from Río Lagartos, at low tide on the wet, sandy beach on the Gulf of Mexico, you can pick up lots of shiny, brown-speckled, inch-long (27mm) snail-like gastropod shells like those shown below:
The shells aren't formed into conspicuous whorls the way we think of snail shells as being, but they whorl a little, as you can see in a close-up of a shell's "closed end" shown below:
Volunteer identifier Bea in Ontario with her new Peterson sea-shell field-guide didn't have much trouble pegging these shells as Common Atlantic Bubbles, BULLA STRIATA. Atlantic Bubble shells commonly turn up on warmer Atlantic beaches from Portugal and the Mediterranean south to the western coast of Africa, to Florida in the US, the Caribbean and Gulf of Mexico, south to northern South America.
Though most bubble-shell species -- members of the genus Bulla -- graze algae in seagrass beds, the Common Atlantic Bubble is thought to be predatory on other mollusks. It burrows in loose sand and mud in estuarine flats and seagrass beds.