A Mystery for Mr. Bass

A Mystery for Mr. Bass is a 1960 children's science fiction novel by Canadian author Eleanor Cameron. The novel followed The Wonderful Flight to the Mushroom Planet (1954), Stowaway to the Mushroom Planet (1956), Mr. Bass's Planetoid (1958), and it was illustrated by Leonard Shortall.

Plot summary
After a record-breaking storm, David and Chuck discover half-million-year-old fossils on the cliffs near their homes where no such bones should be, prompting Tyco Bass to reveal some of the history and customs of the Mycetians, the Mushroom People of Earth. After Tyco's departure, the boys' discovery of the ailing Prewytt Brumblydge's unexpected Mycetian connections leads them to attempt a new, unscheduled trip to Basidium.