Generally large for Sacoglossans, with a broad body that is rounded anteriorly but bluntly pointed posteriorly. The rhinophores are forked (bifid) for varying sections of their length and auricular in most species with the eye spots behind the base. Oral tentacles are present, and are either rounded or pointed.
The cerata are distinctive, most usually being either flattened and leaf-like, wedge-shaped or inflated and can have either a smooth or papillate surface. Sometimes they are very crowded on the dorsum. The cerata may be autotomized at the slightest disturbance to the animal.
The foot is as broad as the body, and generally with a rounded anterior edge. In the genus Cyerce only, the foot is divided by a groove transversely at the anterior third.
The diet is generally green algae.