Horseshoe crabs have roamed the muddy bottoms of salt water harbors and bays for over 300 million years, a time in which the giant prehistoric reptiles and mammals have come and gone. But unlike the dinosaur and mammoth, the horseshoe crab survives today, a "living fossil," which fascinates children at the seashore. But today his long life is being threatened as he is destroyed wholesale by people who do not understand his value in the ecology of the marine life of the shallows. In story form, The Crab from Yesterday details the history and life cycle of a horseshoe crab from its beginning when eggs are deposited on sandy beaches to the reaching of full maturity in the coastal shallows. Young readers, like the boy in the story, will learn that even though some animals lack wagging tails, sticky tongues and happy faces, they can be interesting and appreciated too.