Paracorophium Stebbing, 1899a: 350.
Stebbing, 1906: 663–664.

“Body compressed. Head with produced lateral lobes. Sideplates continuous, 1st not produced forward. Eyes small, on lateral lobes of head. Antenna 1 slender, without accessory flagellum; flagellum with several joints. Antenna 2 robust; flagellum slight, of more than 3 joints. Mandible with 3-jointed palp. Gnathopod 1 as in Corophium, gnathopod 2 nearly as in Corophium, but the long process of the 4th joint fringed on its front or inner margin, while the 5th is fringed on its hind margin, the 2 joints therefore, though fitting together, having no look of coalescence; 6th joint with small palm. Peraeopod 3 the shortest, setose; 6th joint with strong spines. Peraeopods 4 and 5 successively much longer. Uropod 1, and still more uropod 2, stout, with strong spines, biramous, Uropod 3 small, outer ramus nearly as long as peduncle, inner oval, minute. Telson entire, short.”

This genus was established by Stebbing for Corophium excavatum, described by G. M. Thomson (1884) from brackish water in Brighton Creek, near Dunedin, New Zealand. A fuller description of the original species was given by Chilton (1920a) in a paper recording its occurrence in brackish water from Brisbane River, Australia. In his amplified description he drew comparisons between the Australian material, Brighton material, and further specimens from a freshwater lake in the North Island of New Zealand, Lake Rotoiti. In re-examining this material, I came to the conclusion that, although most of the differences which Chilton described as existing between the Rotoiti specimens and the rest could possibly be explained away as due to immaturity or at the most, as he conceded, a distinct variety, yet there are further and more important differences to which Chilton did not draw attention or which he figured without comment.