(Sexton and Spooner, 1940)
Urosome segments 1 to 3 with pronounced rounded dorsal humps each with small groups of spines. Epimeral plate 3 quadrate or weakly produced, posterior margin with 2 or 3 small setules. Head with lateral lobes obliquely truncated, eyes elongate, kidney-shaped. Antenna 1 and 2 short; antenna 1 peduncle sparsely setose, article 1 large and equal to length of 2 and 3 combined, flagellum about twice length of peduncle, up to 25-articulate, very sparsely setose; accessory flagellum about 5-articulate. Antenna 2 in male with peduncle articles 4 and 5 about equal, flagellum densely setose, about 14-articulate, calceoli on articles 2 to 7; antenna 2 in female only sparsely setose and without calceoli. Male gnathopod 1 propodus elongate oval, palm almost longitudinal, median palmar spine separated from group of angle spines. Male gnathopod 2 propodus much broader than 1, palm oblique, median palmar spine separated from angle spines. Gnathopods in female smaller than male, propodus with posterior margin weakly concave, strongly setose, palm almost transverse; female gnathopod 1 propodus short and broad; gnathopod 2 propodus elongate, rectangular. Pereiopods 3 and 4 in male weakly setose; in female densely setose on posterior margin. Pereiopods 5 to 7 spinose, merus broad; pereiopod 5 basis with posterodistal angle freely produced. Male uropod 3 outer ramus densely setose along both margins with plumose setae only on inner margin; inner ramus with few plumose setae. Female uropod 3 outer ramus with plumose setae only on inner margin; outer margin very sparsely setose. Telson, each lobe with 2 lateral spines and 3 apical spines, and pair of small dorsolateral plumose setae.
Male up to 14 mm, female up to 11 mm.
Pale green often with a tinge of brown, pink or blue, and irregular patches of orange on the sides of the pleon and the bases of pereiopods 5 to 7.
Intertidal, upper shore on gravel and shingle especially in areas of freshwater influence, but it also tolerates full salinity.
Around British Isles and west coast of Norway and Brittany.