Styelidae Sluiter 1895

Simple or compound ascidians; tentacles always simple; dorsal lamina always a continuous membrane; branchial folds usually but four (rarely a rudimentary fifth one) on each side; there may be less than four, some or all being obsolete. The simple species often resemble Pyuridae in their thick, tough, wrinkled test, often reddish about the apertures, which are commonly both four-lobed. Stigmata always straight; stomach rather short, rounded or ovate, often with a longitudinally plicated wall and a small caecum, but no hepatic gland. Gonads vary in number from one to many; usually hermaphroditic (sometimes of one sex in the small compound species), attached to the inner surface of the body wall. No renal sac. (Van Name 1945: 219)

Compound ascidians closely related to the Styelidae; test gelatinous, zooids small and arranged in the common test in systems discharging by common cloacal cavities and apertures. Branchial sac with no folds and only three internal longitudinal vessels on each side. Male and female gonads separate. (Van Name 1945: 219)