Tectura fenestrata

How to Distinguish from Similar Species: Tectura scutum usually has a height not more than 1/3 the width, usually has a pattern of blotches, and can grow to more than 5 cm diameter.

Frequently found on smooth boulders surrounded by sand in the mid to lower intertidal.

Geographical Range: Aleutian Islands to lower Baja California

This limpet has an apex as the highest part of the shell, and the height is usually more than 1/3 the width. The apex is anterior to the middle of the shell. The exterior is dark olive or brown, and has no prominent radial ribs. The interior may be dark, but it is not uniformly dark and has an apical blotch. Frequently a dark blue-gray interior margin grades into a dark brown blotch at the apex. The right and left margins are continuously curved without straight margins. The length is usually not more than 1.3 times the width. Usually not more than 2.6 cm long.

Biology/Natural History: Some references show a shell with an interior which is almost entirely white except for a small brown apical blotch; and a pattern of radiating white lines interspersed with brown on the outside. Some say that the apex is slightly off center. This species was formerly considered to be a subspecies of Notoacmaea scutum. The aperture is said to be nearly circular. These limptes often crawl down the surface of the rock to below the surface of the sand at low tide. The name "fenestrata" refers to the checkerboard pattern of white and brown that is seen around the exterior margin of at least some of these limpets. Morris acknowledges the wide diversity of coloration within this species by recognizing two subspecies: A. fenestrata fenestrata, which is grayish green with flecks of pale yellowish. Its inside is bluish white with a narrow brown inside border. A. fenestrata cribraria, the northern form, is dark within the shell. There are many intergrades where the two forms meet.