Janira maculosa

(Leach, 1814)

Body oblong and flattened. Antenna 1 well developed, with a multiarticulate flagellum; antenna 2 very long, longer than the body, with a scale on the outside of the peduncular article 3. Eyes dorsal. Mandible normal, with a strong, truncated molar process. Anterior pereion segments with excavate sides, which, together with the bilobed coxal plates, give the pereion segments 2 and 3 sinuous lateral borders. Pleon of one small, inconspicuous segment, others all fused with the telson to form a large, shield-shaped pleotelson. Postero-lateral borders of pleotelson serrated. Uropods with a peduncle, very long, longer than, or more or less equal in length to, the pleotelson. Adult male with pereiopod 1 normal, subequal to others; preoperculum expanded only slightly at the tip. Coxal plates visible from above on most pereion segments.
Male body length up to 10 mm; females up to 7 mm. Colour yellowish, mottled with red or brown, often with an unpigmented band across the cephalon, anterior to the eyes.

Among sponges, ascidians, coelenterates, polyzoans, Laminaria holdfasts, etc., mainly in dredged material but also between tidemarks.

A subarctic-boreal species most commonly recorded from northern Norway to the Atlantic coast of France, not ranging into the Baltic.