On the Pacific coast, Henricia sanguinolenta is nearly always white to pale orange. The Atlantic form is red, as the species name suggests. It has five arms up to 13 cm long, and an arm-to-disc ratio of 5 to 7. The aboral surface consists of smalt close-set pseudopaxillae with few (3 to 6) to many (25 to 30) spinelets. The papular areas are smalt with 1 to 4 papulae. The marginals are also small and do not form an obvious series. A row of intermarginals varies from a short series to the full length of the arm. Oral intermediates form one or two series, with the longest row reaching to the distal third of the arm. The adambulacrals usually have 10 to 15 (5 to 25) spinelets on each plate, 2 or 3 of these on the edge of the furrow. A short curved spinelet sits on the furrow face.
Taxonomic Note: The taxonomy of this species in the North Pacific is in need of revision. There is disagreement in the literature that remains unresolved. According to Madsen (1987), H. sanguinolenta does not occur in the North Pacific but its close relative, H. tumida Verrill, 1909, does. H. tumida has short stubby arms and its arm-to-disc ratio is from 2 to 2.7. Fisher (1911) examined over 1000 specimens of Henricia from the west coast and determined that many fit the description of H. sanguinolenta. I have also examined specimens with an arm-to-disc ratio of 4.5 to 6.9, which is well out of the range of H. tumida and closer to that of H. sanguinolenta. Madsen did not consider North Pacific specimens in his study, so I am more inclined to agree with Fisher for the purposes of this book . Obviously, more taxonomic work on this species is needed.
Similar SpeciesIn contrast to other Henricia species, this one has small marginals that do not form an obvious series. The arms are generally fat at the base and often there is a crease where the arm joins the disc. Within diving depth this is the only white