While Huxley and Lewis may have disagreed, their writing suggests they were both coming to some kind of middle ground. Neither was an extremist. Lewis welcomed scientific advance and saw no reason why biological evolution should clash with his spiritual beliefs. Huxley was a rationalist who, through his own experience, came to have a mystical worldview.
As such, in symbolic terms they correspond well to the heads of the twin serpents, which represent the resolution of opposites where they meet over the Abyss.
Huxley and Lewis: both influenced by The Marriage of Heaven of Heaven and Hell, both writing about the nature of spirituality, both dying on the same day. When connecting them to the evolving symbolism, there is another factor of great relevance. News of their deaths was overshadowed by that of a much more prominent world figure.
November 22 is the day John F Kennedy was assassinated.