The species here described is the first representative of the family Sternaspidae found in Brazilian waters. DIAGNOSIS - Sternaspis capillata sp. n. is a small species, not longer than 20 mm when fully distended. Oral segment well formed with a conspicuous prostomium. Setae of the anterior region strong, bent and spatulate, of metallic colour, golden. Eight median segments with little bundles of capillary setae. Ventral shield formed by two different plates, with no external visible sculpturing and covered by fine mud. Twenty bundles of setae emerge on each side under the shield, those of the eleventh pair four times longer than the nearest ones. The branchial region is densely covered by very thin and long papillae, up to the margin of the ventral shield. The branchiae are 15 to 20 in number on each side and are not grouped in plates. The family is considered by many authors as having only one cosmopolitan species S. scutata (Ranzani) 1817. The incomplete descriptions of the greater part of the 14 species mentioned in HARTMAN'S "Catalogue" renders it difficult to appreciate their validity. S. capillata sp. n. diverges from the species mentioned in HARTMAN'S "Catalogue" by the number of setae of the anterior segments, by the exceptional development of setae of the 11th posterior pair and by the presence of numerous, long, filiform papillae covering the branchial region. I consider the species near to S. laevis Caullery 1944, described from Malasia and known only from its original description.
