The constellation you might be thinking of is Cancer the Crab. It is a small and faint constellation located in the Northern Hemisphere, near the constellation Gemini. It is named after the crab that, according to Greek mythology, attacked Hercules during his battle with the Hydra.

Cancer is not particularly notable for its shape, but it is known for containing the star cluster Praesepe, also known as the Beehive Cluster.