Jellyfish diameter; the tentacles and mouth parts usually extend beyond this bell dimension. The smallest jellyfish are the peculiar creeping jellyfish in the genera "Staurocladia" and "Eleutheria", which have bell disks from to a few millimeters in diameter, with short tentacles that extend out beyond this, which these jellyfish use to move across the surface of seaweed or the bottoms of rocky pools. Many of these tiny creeping jellyfish cannot be seen in the field without a hand lens or microscope; they can reproduce asexually by fission (splitting in half). Other very small jellyfish, which have bells about one millimeter, are
Lion's mane jellyfish lion's mane jellyfish. This was later corrected – in 1864, a bootlace worm ("Lineus longissimus") was found washed up on a Scottish shore that was long. ("That" claim has its critics: because bootlace worms can easily stretch to several times their natural length, it is possible the worm did not actually grow to be that length.) Lion's mane jellyfish The lion's mane jellyfish, also known as the giant jellyfish or the hair jelly, is the largest known species of jellyfish. Its range is confined to cold, boreal waters of the Arctic, northern Atlantic, and northern Pacific Oceans. It is common