The first antennae, or antennules, are held on a long flexible stalk, and are used for sensing the environment. The second antennae are the slipper lobsters' most conspicuous feature, as they are expanded and flattened into large plates that extend horizontally forward from the animal's head.

There is considerable variation in size among species of slipper lobsters. The Mediterranean species Scyllarus pygmaeus is the smallest, growing to a maximum total