White color (Borradaile, 1903)
Characters of Sewynia: (1) Carapace broadly oval, without teeth or notches on the anterolateral edge, flat, but falling away in front. Body rather deep. (2) Front narrow, bent downwards, bilobed owing to a deep groove in the middle, continued into the interantennular septum. (3) Eyes well formed and well pigmented, small, stout, not fixed into the small, close-fitting orbits. (4) Antennules fold almost, but not quite, transversely. (5) Antennae short, the flagellum standing in the orbital gap. (6) Third maxillipeds with meropodite roughly square, a little smaller than the ischiopodite; palp strong, arising nearly in the middle of the fore edge of the meropodite ; and exopodite well developed. (7) All the legs present and stout. (8) Abdomen not nearly covering the last thoracic stemite.
" A Selwynia with the body smooth and naked except for some hairs on the underside and on the last three joints of the walking legs, microscopically pitted all over; the regions of the back barely to be made out, the chelipeds very large and stout, their fingers nearly as long as the palm, gaping slightly, finely toothed on their opposed edges, and not furrowed ; no thorns or teeth on any of the joints of any leg, save a small tooth underneath the meropodites of the walk-ing legs ; and the walking legs very stout, with very small end-joints, the last pair being a good deal smaller than the rest." (Borradaile, 1903)
Length of the only specimen (a male) : 6 mm. Breadth : 8 mm. (Gardiner, 431)
