Sigh. Huxley and Sagan were great science educators. But the current Chief of the Division of Invertebrate Studies and Curator of Crustacea at the Los Angeles County Natural History Museum (Joel W. Martin, PhD Marine Biologist with numerous books and articles to his credit, mainly about the natural history and evolutionary relationships of decapods and brachiopods; got his bio off Wikipedia) considers Huxley and Sagan's story about how the heikegani 'probably' came to so resemble angry samurai's via enhancement of a faint resemblance by superstitious Japanese fishermen to be a modern myth. The pattern of ridges are functional as muscle attachment points and similar patterns are found on the carapaces of other species and in the fossil record. I think I'll go with a relatively obscure but actual expert and specialist on the matter over famous but more generalist science popularizers in this particular case, despite my gratitude for their many accomplishments and contributions. They didn't study the heikegani, they knew of it and proposed a reasonable explanation for its unusual carapace pattern. That explanation happens to be incorrect.
I'm not anti-Christian. I'm anti-stupid.