At forty-feet in length, this "blob" would have to have come from a Basking shark at the upper reaches of the species' achievable size; from an animal that big, there ought to be some clearly recognizable structures left. It doesn't seem reasonable to believe that a decomposed, 40-foot Basking shark could fool any ichthyologist these days, since they tend to top the suspects list when weird carcasses are found.
Spotted next to an expired humpback whale, eh? Odd. A gray and lumpy mass, not foul-smelling, floating in close proximity to a whale. Could this stuff have been coughed-up or pooped-out of the dying humpback, ala ambergris?