Stapelia. See more pictures of cacti.
Though they prefer bright light, they can sunburn in hot summer sun. They are shallow rooted and do not care to be crowded. The soil should have excellent drainage. Do not overwater -- drench and then let dry between waterings.
In the winter, water only enough to keep the plants from shriveling. They grow easily from seed; the shoots, cut off at the thinnest part, will root easily.
Learn how to care for cactus plants: