Box jellyfish box-like bell, from which its name is derived. From each of the four lower corners of this hangs a short pedalium or stalk which bears one or more long, slender, hollow tentacles. The rim of the bell is folded inwards to form a shelf known as a velarium which restricts the bell's aperture and creates a powerful jet when the bell pulsates. As a result, box jellyfish can move more rapidly than other jellyfish; speeds of up to per minute have been recorded. In the center of the underside of the bell is a mobile appendage called the manubrium which
Irukandji jellyfish fatal, but two people in Australia are believed to have died from Irukandji stings in 2002 during a rash of incidents on Australia's northern coast attributed to these jellyfish—greatly increasing public awareness of Irukandji syndrome. It is unknown how many other deaths from Irukandji syndrome have been wrongly attributed to other causes. It is also unknown which jellyfish species can cause Irukandji syndrome apart from "Carukia barnesi" and "Malo kingi". Irukandji jellyfish Irukandji jellyfish ( ) are any of several similar, extremely venomous species of box jellyfish. With an adult size of roughly a cubic centimetre (1 cm), they are