Tresus Gray 1853

The clam is buried in sand; its siphons extend upward on stalks. The shell may measure 150 mm. Depth 9 m. Washington clams make a very tasty dish.

The shell of Tresus capax has a large gape at the posterior end to accomodate the large siphons

Because of the large siphons, Tresus capax has a very deep pallial sinus. It has a continuous pallial line. Note also the almost equal-sized anterior and posterior adductor muscle scars. The posterior end is to the left.

The shell is less than 1.5 times as long as it is wide.

The umbo is about 1/3 the way from the anterior (left) end of the shell. The hinge (to the right of the umbo) is thin

Boring clam siphons photographed at 7 m depth.

There is a shelflike chondrophore and several hinge teeth on both hinge plates. Top = right valve, bottom = left valve. Anterior is to the right.

The gouge on the siphon of this individual is due to a bite by the predatory hairy triton snail Fusitron oregonensis.

This individual from March Point has a shell length of 19 cm and shell height of 11 cm. It has retracted its siphon about as far as it can but before retraction the siphon was 18 cm long, or about as long as the shell.

On some mud flats the tips of the large siphons, which are exposed at the surface when feeding, become overgrown with red algae such as Polysiphonia, as seen here. Photo by Dave Cowles 2007

Tresus capax from Padilla Bay, WA. Scale is cm (Photo by: Dave Cowles, July 2005)