Solaster dawsoni is usually a homogeneous brown, with an evenly textured aboral surface. It has 11 or 12 arms (sometimes 8 to 13) and can grow up to 20 cm in radius. The ratio of arm to disc is from 2.5 to 3.4. Its body is occasionally red, orange, or mottled brown and beige. When viewed from above, the inferomarginals appear as serrated edges of the arms. The aboral pseudopaxillae are round and flat-topped with 30 tiny spine lets on the perimeter and up to 15 central spinelets. The superomarginals are similar in shape but larger. The oblong inferomarginals are three to four times wider than their length. The oral interradial area is small (only 20 to 25 plates) when compared with the three other species in this genus. The adambulacrals have a furrow series of 3 or 4 long, tapering spines; the oral surface bears a straight transverse series of 3 to 6 long spines that stand about twice as high as the spines on the adjoining inferomarginals and slightly higher than the furrow series. Each pair of mouth plates is rather broad and shovel-like with 9 to 11 marginal spines, the apical spine being largest. Spines on the oral surface can vary, from 1 or 2 suborals to a double row of 5 to 10 spines.
Characteristics
Similar SpeciesThe living colour and body shape of the four species of Solaster in British Columbia are fairly distinctive, but if specimens are dried you may need to consult the descriptions of the adambulacral spines.