Hydrozoa (Hydrozoans)
Hydrozoa (hydrozoans) are a taxonomic class of very small, predatory animals which can be solitary or colonial and which mostly live in saltwater. A few genera within this class live in freshwater. Hydrozoans are related to jellyfish and corals and belong to the phylum Cnidaria.
See: http://en.wikipedia.org/wiki/Hydrozoa

A hydrozoan anatomy
Source: http://animaldiversity.ummz.umich.edu/site/resources/Grzimek_inverts/Hydrozoa/v01_id118_con_hydanat.jpg/view.html

Medusa MM250 | 
Plumalina MŠ6038 | 
Plumalina MŠ6038 | | |
In the Virtual Museum there are total
64 samples