Days of the Dolphin: Cetaceans in Cold War Science and Science Fiction (Part One) by Michael Grasso does not get around to giving examples of dolphins in science fiction. We have to wait for the sequel, which Grasso promises to offer soon. But his summary of the research of John Lilly leaves little doubt in my mind that Lilly's writings helped inspire the character of Howard the dolphin in Illuminatus! Lilly and RAW were mutual admirers, so I was interested in Grasso's piece.
Thanks to Jesse Walker for calling my attention to the piece.