Tiny snail

Responding to my last post, snail maven Aydin Örstan thought the third of the terrestrial snails harboring on the marine snail shell in my backyard was Vallonia costata. If so — and it looks like it to this mollusk amateur — that would make for five different species of snails found in my concrete slab of a Brooklyn backyard so far.

This snail is tiny, 2mm across, and posed here on FDR’s eye on a dime. My antique snail book, Shells from Cape Cod to Cape May with Special Reference to the New York City Area (Dover, 1971, reprinting a 1961 original) by Jacobson and Emerson, notes that this Eurasian species wasn’t reported in the NYC area until “recently” when some were found in the Bronx, in a colony subsequently destroyed by construction. Jacobson and Emerson inform me that the ridge-like axial ribs on this shell are also known as costae.The hollow at the center of the whorl is called an umbilicus.