Shell small, thin, long and narrow, the sides parallel; apex at the anterior fourth or third. Surface smooth, shining, having light growth-lines. Very light brown, with narrow dark brown stripes radiating from the apex and from the ridge of the back, where they form a series of v's. Inside bluish-white, showing the color pattern of the outside through the shell. Length 11, breadth 4, alt. 3 mill.

Shell small (<15 mm in length), medium profile, light yellow with brown-red chevron markings, sculpture of concentric growth lines, aperture laterally compressed or oval (rare). Lateral teeth short, with straight cutting edges, lateral teeth aligned diagonally across ribbon segments. Animal lacks pigmentation. Low intertidal on the eel grass Zostera marina in estuaries (compressed form); oval form along subtidal open coast.

Resembles no species but A. paleacea. The long narrow form is caused by growth on Zostera fronds. There is some variation in the coloring, broad bands sometimes replacing the narrow lines. The front end is generally of a decidedly darker shade. A specimen of average proportions is figured.

Santa Barbara, Monterey, San Diego, California.
Mugu Lagoon, California (34°06'N) to Cabo San Lucas, Baja California, Mexico