J. R. R. Tolkien

Hobbits are an unobtrusive but very ancient people, more numerous formerly than they are today; for they love peace and quiet and good tilled earth: a well-ordered and well-farmed countryside was their favourite haunt.

Giant squid aren't rare. Based on the number of beaks that have been found in the stomachs of sperm whales, it's thought that there are actually millions of them in the ocean, and yet, we haven't seen them.