The cluster anemones are a group of closely related species of sea anemones that are found in the intertidal zone of rocky shores. There are two main species of cluster anemones: the common cluster anemone (Anthopleura elegantissima) and the giant cluster anemone (Anthopleura xanthogrammica).

The common cluster anemone is the most common of the two species and is found on rocky shores throughout the world. It is a small anemone, typically growing to a height of 2-3 inches. The common cluster anemone has a bright green body with white or pink tips.

The giant cluster anemone is less common than the common cluster anemone and is found only on the Pacific coast of North America. It is a much larger anemone, typically growing to a height of 6-12 inches. The giant cluster anemone has a bright red body with white or pink tips.

The common cluster anemone and the giant cluster anemone are very similar in appearance, and it can be difficult to tell them apart. However, there are some key differences between the two species. The common cluster anemone has a smooth body, while the giant cluster anemone has a warty body. The common cluster anemone also has a single row of tentacles, while the giant cluster anemone has two rows of tentacles.

Despite their similarities, the common cluster anemone and the giant cluster anemone are two distinct species. They have different geographic ranges, and they have different body shapes and tentacle arrangements.