There are only six described species world wide with the most recognisable being the large species Umbraculum umbraculum. It carries a flattened circular shell upon the dorsum that is much smaller than the body and which is most often covered in various forms of sessile marine life.
The bulky circular shaped body is covered in large soft tubercles that are neither retractable nor the bearers of acid glands. These tubercles are white whilst the body colour may range from red to brown to yellow even colourless depending on location and probably its food source.
It has a deep mid-anterior vertical cleft in the foot and body containing the mouth, oral tentacles and non-retractile penis. This deep cleft has to open to enable the broad radula, which does not evert, to bear against the food source. The circular foot has a smooth and flat sole. The body does not elongate when the animal is crawling. There are two pairs of rolled head tentacles with longitudinal slits. The anterior oral tentacles are located either side of the mouth in the cleft. The other pair, the rhinophores, is larger, carried higher and have the eye spots situated in between them. They protrude from under the shell and are the best clue to finding the anterior end of the animal.
The gill runs from the front along the right side in a space under the shell and is observable. The anus is located posteriorly.
Diet consists of a variety of sponges. Reported to live longer than a year.