Everytime I think I have Caribbean ID's pretty well in hand someone throws out a photo that I can't be sure of. If you can find eyespots, then most of the look is hummelincki/filosus but that is more from elimination than visual id. The color is wrong for a merc and it has too many papillae (the bumps on the skin). The arms taper too much for brieareus (as well as wrong coloration). We don't see many vulgaris (this name is misused more times than it is correct) and I have only see a couple in real life but I think their arms would be longer and thicker and I don't think they show as many papillae. The sucker rings DO seem to have an outer blueish ring (common to hummelincki/filosus and the Indonesian aculeatus - among others but not the ones mentioned above - not sure on vulgaris). I think it is the mantle/eye proportions that keeps me from being cofident.