Flat body. Prominent marginals; the supero- and inferomarginals are similar. The aboral plates are flat or paxilliform, bearing granules, low stumps or spines. Only the radial areas have papulae. Pedicellariae are generally present. The tube feet have suckers.
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Ceramaster arcticus is small and pentagonal, stiff and firm to the touch, and up to 5.5 cm in greatest radius. It is pale orange with red patches. The ratio of arm to disc is 1.6. The aboral surface has tabulate plates bearing 4 to 12 marginal granules surrounding 1 to 3 smaller central granules. C. arcticus has 18 to 24 massive superomarginals, each usually with a bare spot surrounded by flat granules; the inferomarginals each have a smaller bare spot; papulae cover the aboral surface. The adambulacrals have 2 or 3 short, thick furrow spinelets with 3 to 6 granules on oral surface of the plate, which often has a bivalved pedicellaria.
Ceramaster arcticus differs from C. patagonicus in its smaller average size, fewer granules on the aboral tabulate plates and fewer adambulacral spines.
Bering Sea to the Juan de Fuca Strait; intertidal to 186 metres. Found on mud in the deep part of its range to rock in shallow waters. Rare in this region (the area from Glacier Bay to Puget Sound to a depth to 200 metres).
Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2019. E-Fauna BC:
Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab
for Advanced Spatial Analysis, Department of Geography, University of British
Columbia, Vancouver. [Accessed:
2020-08-08 9:41:13 PM]
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