(O. Fabricius, 1780)
The body is rather slender, especially in the male, with a maximum length of 12 mm. The bilobed carapace is large and covers the thorax and part of the abdomen and bears anteriorly a distinct, hinged rostral plate, which is laminar and without a terminal spine and covers the head. The eyes are well developed, red in living animals. The first antennae in both males and females are shorter in length than the second antennae. In males, the second antennae are elongated, being as long as the entire body. The thoracic appendages are all foliaceous and similar in form. The first four pairs of pleopods are biramous, the last two uniramous and rudimentary. The seven-segmented abdomen terminates in a caudal furca. The furcae are narrow, longer in males than in females.
Restricted to coastal waters at depths of 5-60 metres.
Occurs in coastal areas throughout the North Atlantic extending from eastern North America, east and west Greenland, Iceland, Faeroes and Norway to Spitsbergen. Also in the Kattegat, North Sea, English Channel and extending southwards into the Mediterranean where it has been found on the coast of Italy.