I'm looking for two childrens books from the 1970s: A young boy in a library reading a book about a unicorn in a wood falls asleep to find himself with the unicorn in said wood. Then goes on a 'quest' encountering other mythological creatures: manticore and cockatrice, phoenix, griffen and a mermaid who tries to charm them with her song! Had b&w illustrations and each creature was encountered each chapter. A fisherman/sailor meets a green skinned boy from the sea who gives him a charm(tooth/Shell) that enables him to breathe underwater! b&w illustrations. Very grateful for the help!