Cubozoans
The (a) tiny cubazoan jelly Malo kingi is thimble shaped and, like all cubozoan jellies, (b) has four muscular pedalia to which the tentacles attach. M. kingi is one of two species of jellies known to cause Irukandji syndrome, a condition characterized by excruciating muscle pain, vomiting, increased heart rate, and psychological symptoms. Two people in Australia, where Irukandji jellies are most-commonly found, are believed to have died from Irukandji stings. (c) A sign on a beach in northern Australia warns swimmers of the danger.
Source
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"OpenStax College, Biology. November 17, 2013."
http://cnx.org/content/m44664/latest/?collection=col11448/latest
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