The Gem Shells

THE GEM SHELLS Genus GEMMA, Desh.

Shell minute, rounded or sub-triangular, equilateral; margins crenulated within; hinge short, narrow; muscle scars ventral pallia; sinus vertical. Very small clams abundant on the Atlan tic coast.

G. gemma,

Totten, about the size of a pea, with elevated beaks, and furrowed, violet-tinged white shell, is a well-known species. A colourless variety with beaks much elevated, abounds

from Cape Cod to New York Bay. The gem shell of San Fran cisco Bay was introduced with seed oysters from Chesapeake Bay. G. purpurea, Lea, is the same species.

Habitat.— Labrador to Cape Hatteras.