A family in the subclass Raptoria. The common name is "rain tiger", also known as "sea piglet". The adult shell is completely degraded or is an inner shell, plate-like or axe-shaped, with limestone or only the cuticular membrane. The body is ovoid or slug-shaped. The head has a pair of antennae in the form of ears; the head and neck are distinct, with a pair of ear-shaped olfactory horns. Gastropods are broad with a caudal posterior end, so named because they resemble sitting rabbits when at rest. It is widely distributed in the warm waters of the world, and 19 species are known in China. Sea hare genus lateral foot developed, front and rear end free, can be used as a swimming organ. There are purple juice glands, can launch purple juice to kill small animals or escape from the enemy. The main food is seaweed.