The family Convolutidae includes acoels with a ventral mouth opening and a body-wall musculature composed both dorsally and ventrally by circular, longitudinal, and longitudinal crossover muscle fibers. The ventral body wall also has a group of U-shaped fibers. Most species are symbionts with algae. The anterior end has a cluster of frontal glands, a pair of eyes and a statocyst. The body has pigmented lens. Intestine and excretory system is absent. It is hermaphrodite but protandry is common.
There are over 100 species recognised in the family Convolutidae: