National Geographic : 1959 Sep
Florida Sands Yield a Secret of the Sea Ken and Pat Libby, children of the author, find a mermaid's purse on St. Augustine Beach. Their father spent two years studying the strange birth proc ess of its maker, the humble clearnose skate. Gulls, clamoring for a hand out, flock around the children. Within the rubbery purse, a baby skate grew like a chicken in an egg. After the embryo hatched, the sea washed the case ashore.