Sometimes white paper is too white, or there was just a bit of board siting around, and so was turned into substrate.  The central so-called King Crab is not a crab or a king - at the time this image was printed it was described as Xiphosura or Limulus polyphemus , which is a nomenclatury a bet both ways.  That dagger like projection is a telson.  The male is towed to shore by the female, probably not to save him from drowning.  The eggs are buried in the intertidal sand,.there are no reports of games of tennis, or them being eaten by large storks or becoming lobster food, at least not that I’ve read.