These jellies are commonly referred to as Dinner Plate Jellies because their platter-like bell can reach an overall size of 20 cm or nearly 8″.  They are unusual among medusas in that they actively search for their prey, rather than relying on the fortune of having copepods, other cnidarians and ctenophores and/or salps cross their path.  At one point the jelly photographed here would have been identified as a Solmissus marshalli, but it is now considered part of a species complex.  For a more thorough discussion of Solmissus taxonomy in the Salish Sea, see discussion between C.E. Mills and D. Lindsay on inaturalist.