Seanet High Intertidal

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Chthamalus spp.
Phylum Arthropoda, Subph. Crustacea, Class Thecostraca, Subcl. Cirripedia, Order Thoracica, Family Chthamalidae

Acorn barnacle; small, brownish white to gray; to 8 mm diameter, 6 ~equal size shell plates, smoother than Balanus glandula; lacks calcareous basal plate. Two local species (C. dalliC. fissus) cannot be distinguished easily in the field.

Abundant, high to upper mid-intertidal zones, exposed outer coast to protected bays.

Geo Range: Chthamalus dalli Alaska to San Diego; Chthamalus fissus: San Francisco to Baja
Synonyms:
Similar species: C. fissus sometimes possesses a slit-like aperture (arrow); setae at ends of 2nd cirri coarsely bipectinate. Setae at ends of 2nd cirri in C. dalli are finely bipectinate.

Image:
form with slit aperture (arrow) is Chthamalus fissus.

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