noun - The compass jellyfish is a very common species of jellyfish that lives in coastal waters of the Atlantic and Mediterranean Seas, including near the United Kingdom and Turkey. It has a diameter of up to 30 cm. Its 24 tentacles are arranged in eight groups of three. It is usually colored yellowish white, with some brown.
It occurs in coastal waters all round the British Isles. It is prevalent off the south and west coasts of England and Wales. It has been recorded off the Cumbrian coast, the Isle of Man and off the north coast of Ireland.
The compass jellyfish has a saucer-shaped bell, with 32 semi-circular lobes around the fringe, each one with a brown spot. On the upper surface of the bell, 16 brown V-shaped marks radiate outwards from a dark central spot. The mouth, the only opening to the exterior, is located on the centre of the underside of the bell, and is surrounded by 4 arms.
The compass jellyfish may be confused with the common jellyfish when stranded. Aurelia aurita have shorter tentacles with no brown v-shaped markings on the bell. Instead it has 4 purplish-blue horseshoe shaped gonads that are easily distinguished through the upper surface of the bell. The stinging cells and venom can produce painful, long lasting weals in humans.