The Field Guide is a book that only appeared in the episode "Tea at the Treedome." It is known to contain an image of a "Land Squirrel."
The Field Guide appears to be a blue book with a picture of a black anchor on it. The words "Field Guide" is written at the top in white letters.
Role in the episode
While Jellyfishing one day, SpongeBob comes across a strange creature at the bottom of a cliff. The creature is wrestling a Giant Clam. SpongeBob consults the guide and finds out that the creature is a Land Squirrel.