Family Gammaridae Leach.

Gammaridae Stebbing, 1906: 364.

“Body more or less slender, pleon segments 4–6 usually well defined Antennae generally rather slender and, as a rule, but little different in the two sexes; accessory flagellum of antenna 1, often greatly developed, may dwindle sometimes to a single joint or tubercle, or disappear entirely. Mouthparts normal. Upper lip with a rounded, entire or only slightly emarginate distal border; lower lip with inner lobes well developed, slightly indicated or absent. Mandible with dentate cutting edge and accessory plate, spine-row, molar and 3-jointed palp (only in one genus 2nd joint smaller than 1st). Maxilla 1 with inner and outer plate and 2-jointed palp (only exceptionally 1st joint as large as 2nd). Maxillipeds with inner and outer plates and palp well developed Gnathopods 1 and 2 generally rather powerful, rarely less than subchelate, seldom both weak; sometimes stronger and larger in male than in female. Peraeopods more or less

slender, sometimes stout, sometimes 2nd segment in peraeopods 3–5 little expanded. Pleopods lose only by exception one ramus and uropod 3 one or both of the rami. Uropod 3, rami more or less foliaceous, projecting beyond uropods 1 and 2; uropod 3 and telson never hooked. Telson either with entire margin or cleft to the base, sometimes strikingly different in the two sexes.” (Stebbing.)

In constructing keys for this family, my suspicion that the New Zealand representatives need considerable revision was amply confirmed. However, most of the species are readily identifiable with the aid of Chilton's and Stephensen's papers.