Body strongly dorsoventrally flattened and oval, especially in male; pleon laterally flattened and flexed beneath pereion. Coxal plates very short and not overlapping. Eyes protruding, rounded. Antenna 1 peduncle article 2 slightly longer than article 3. flagellum about 6-articulate in male and 4 or 5-articulate in female; accessory flagellum small, 1-articulate. Antenna 2 longer than antenna 1 especially in male, peduncle article 5 longer than article 4, flagellum 4-articulate. Gnathopod 1 small, strongly setose, propodus oval, palm poorly delimited, dactylus elongate with the inner margin coarsely toothed. Male gnathopod 2 basis with a pair of small anterodistal lobes, merus setose with a stout distal spine, propodus extremely large and robust, elongate oval, anterior margin spinulose, palm occupying most of the posterior margin, palmar margin with a small rounded lobe and a blunt process close to the base of the dactylus; posterior margins of ischium, merus and propodus with many plumose setae. Female gnathopod 2 without plumose setae; merus with a stout distal spine, propodus broadly oval, anterior margin spinulose, palm setose and delimited by a pair of long spines, dactylus robust and as long as the propodus. Pereiopods robust, setose, dactylus strongly developed; pereiopods 6 and 7 basis with only a small posterior lobe. Uropods 1 and 2 biramous, strongly spinose, rami with a long apical spine. Uropod 3 very small, rounded. Telson with a few long dorsal setae.
Up to 4 mm.
Often quite striking, dark red or brownish red, sometimes with a large patch of purple or lilac.
Intertidal and shallow subtidal, often found in low level rock pools, especially amongst Corallina species.
English Channel; Atlantic coast of Europe and North Africa; Shetlands to the Mediterranean.