Genus Jaxea Nardo, 1847

Laomediids with a firm, white exoskeleton covered with a densely crowded fur of very short setae. The linea thalassinica of the carapace is distinct and well page 4 developed. The eye is reduced and hidden under the rostrum in dorsal view and the pigmentation of the cornea is reduced. The peduncles of both the antennules and antennae are greatly elongated and relatively slender. The scaphocerite is rudimentary but distinct. First maxilliped with flagellum on exopod but no podo-branch. First pereiopods subequal, with enlarged and elongate chelae, 2nd and 5th pereiopods subchelate. A single arthrobranch on 1st maxilliped and two on 2nd and 3rd maxillipeds and on 1st to 4th pereiopods. Podobranch present or absent on 3rd pereiopod. Male 1st pleopods absent, female 1st pleopods reduced and uniramous, 2nd to 5th pleopods biramous and similar in both sexes.

The type of the genus is Jaxea nocturna Nardo, 1847 (of which Calliaxis adriatica Heller, 1863, is a synonym) known from the British Isles and Irish Sea (Selbie, 1914), the Mediterranean coast of Spain (Zariquiey, 1946), the Adriatic (numerous authors), and apparently more abundant in the eastern Mediterranean, including the coasts of Israel and Egypt, than in the western Mediterranean (Holthuis and Gottlieb, 1958).

A fossil from the Miocene of the Vienna Basin has been described as Jaxea kuemeli Bachmayer, 1954 (corrected from kümeli). It can be distinguished at once from the two named recent species in this genus by the position of the cervical groove in the adult stage. In the fossil form this groove is situated distinctly posterior to the midpoint of the carapace, exclusive of the rostrum.

A Key to Adults of Known Recent Species of Jaxea

Hand between 1 and 1½ times length of carapace and rostrum; fingers more than 1½ times length of palm. Anterolateral margin of carapace with several small teeth below origin of line a thalassinica and sometimes several minute "thorns" above. Third maxilliped with ischium armed medially with a crest of about 14 to 16 strong teeth	J. nocturna
Hand subequal in length to carapace and rostrum; fingers a little longer than palm. Anterolateral margin of carapace with single small tooth immediately above origin of line a thalassinica and sometimes several minute "thorns" below. Third maxilliped with ischium armed medially with a crest of about 12 to 14 (usually 13) strong teeth	J. novaezealandiae