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Family Semelidae

SHELL thin, almost equivalve, gaping and usually flexuose behind; ligament external, short; cartilage in the cardinal pit; siphons long, divergent.

Genus SEMELE, Schum.

The Rayed Semele (S. radiata, Say) has flat, circular valves, a bit concave on the posterior side, colourless or rayed with bands of rose colour. Lining yellow. Length, 1 inch.

Habitat.--Geogia southward.

The Rock Semele (S. rupium, Sby.) with a pink hinge area, is a pretty species of Southern California. Length, 1 inch.

The Clipped Semele (S. decisa, Conr.) has its circular outline clipped behind in a straight line. The brown, wrinkled exterior is unattractive, but the shell lining is china-like, tinged purple, darkening to the lips. Length, 2 inches.

Habitat.--Southern California.

S. Californica, Ads., is a rare, yellow species an inch across. S. rubro-picta, Dall, has an irregularly cross-ridged surface rayed with purplish rosy bands. Inside, the thick valves are yellow or white. These two species are found in the same locality.

Habitat.--San Diego, Cal.

Genus CUMINGIA, Sby.

Shell ovate-triangular, broadly rounded in front, white, equilateral; surface marked with elevated growth lines.

C. tellenoides, Conr., ranges from Cape Cod to the West Indies. Specimens I studied alive at Woods Holl were taken from a thin stratum of soft mud in water three feet deep. The station of these interesting little clams is known only to Mr. George Gray, the veteran collector for the Marine Biological Laboratory, who knows the sea bottom of that region, and the inhabitants thereof, as a cook knows her pantry shelves.

It was August, and the ventricose shells of the female were tinted pink by the mass of eggs under the transparent valves. In a dish of clear sea water the two siphons were soon thrust out at the pointed end of the shell. The broad foot steadied the valves on edge, while the siphons waved aimlessly up and down. They are like transparent, pink tubes, no larger when extended than a coarse thread. The upper, excurrent tube was two inches long when fully extended. The other was one-fourth as long. Eggs were discharged in a stream by the females. These were delicate, pink spherules, just visible to the unaided eye. Some shells were warped by growing in rock fissures. Length, 1/2 inch.

C. Californica, Conr., twice as large, with ridged growth lines, represents the genus on the coast of Southern California.

Genus CERONIA, Gray

Shell ovate wedge-shaped, truncated behind.

C. Arctica, Conr., has thick, strong, smooth, sub-triangular valves, white under a yellow epidermis. The hinge has a V-shaped primary tooth with a long, striated lateral tooth on each side of it. Length, 1 1/2 inches.

Habitat.--New York Bay northward.