Staurozoa

The Staurozoa are a Class in the phylum Cnidaria. It includes the stalked jellyfish. It was an order within the Class Scyphozoa, but recent genetic work has shown it to be a class of its own. This is a small class of about 50 species, mostly inshore and quite small. The recent discovery of some Staurozoa near deep sea hydrothermal vents was a surprise, and makes it clear that there is much more to learn about them.
The Staurozoa are unique in not having an alternation of polyp and medusa life cycle phases. They have an attached "medusa" stage, with a life style looking rather like polypoid forms. 
Members of this class are commonly found in relatively cold waters, close to the shoreline. After the larvae crawl across the sea floor and find a suitable place, they attach themselves to rocks or algae.