![Thumbnail: [Volume 82, 1954-55 page 432]](/journals/rsnz/images/rsnz_82/thumbnails/rsnz_82_02_0484_0432_ac_02.gif)
Stebbing, 1906: 685.
“Body depressed throughout. Head with narrow lateral lobes. Sideplates small, discontinuous, 1st conically produced, tipped with setae. Eyes small or imperfectly developed, on lateral lobes of head Antenna 1 without accessory flagellum; flagellum slender, with several joints. Antenna 2 strong, pediform, usually much longer in male than in female; flagellum short, 3-jointed, with apical hooked spines. Upper lip broad. Lower lip normal. Mandible with 2-jointed palp, slender, each joint carrying a strong plumose seta; other parts normal. Maxilla 1, inner plate nearly obsolete, outer with 7 spines on apical margin, 2nd joint of palp long. Maxilla 2, inner plate fringed on inner margin. Maxillipeds, inner plates narrow, without apical spine-teeth, outer long, narrow, with slender spines on inner margin; finger of palp small, with apical spine. Gnathopod 1 slender, the short projecting 3rd joint and long 5th densely fringed with long setae; 6th joint narrow with short palm Gnathopod 2 rather larger, 4th joint closely attached to hind margin of 5th; its own convex hind margin fringed with very long plumose setae in 2 rows; 6th joint sublinear, without palm Peraeopods 1 and 2, 2nd and 4th joints somewhat expanded, 5th very short; finger slender Peraeopods 3 and 4, 2nd joint moderately expanded; 4th produced in front of the short 5th, which carries 2 oblique rows of spines, 6th slender, not long; finger short, reverted. Peraeopod 5 long and slender, 2nd joint fringed on both margins with long setae. No branchial vesicles on gnathopod 2. Marsupial plates narrow. Pleopods 1–3, peduncle greatly expanded on inner side, the 2 coupling spines with several teeth; inner ramus the longer, without cleft spines on 1st joint. Uropods 1 and 2, rami rather short, with strong spines on outer margin Uropod 3, peduncle short, ramus single, laminar, With some fringing setae. Telson entire, small, distinct.”
![Thumbnail: [Volume 82, 1954-55 page 433]](/journals/rsnz/images/rsnz_82/thumbnails/rsnz_82_02_0485_0433_ac_02.gif)
| 1. Segments of urosome fused; uropod 1 attached ventrally; lateral margins of urosome without notches* | C. acutum |
| Segments of urosome fused; uropod 1 inserted in notch in the lateral margin* | 2 |
| 2. Antenna 2, segment 4 with a large terminal tooth and a smaller one above (male) | 3 |
| Antenna 2, segment 4 armed only with spines (female) | 4 |
| 3 Antenna 1, flagellum of 5 segments, shorter than 2nd segment of peduncle; antenna 2, segment 4 with 2–3 spines, segment 5 without processes | C. sextonae, (male) |
| Antenna 1, flagellum of 7–10 segments, longer than 2nd segment of peduncle; antenna 2, segment 4 without spines, segment 5 with 2 processes | C. acherusicum (male) |
| 4. Antenna 2, segment 4 with spines set in a single row | C. sextonae (female) |
| Antenna 2, segment 4 with all spines, except the terminal one, set in pairs | C. acherusicum (female) |
With the aid of Crawford's and Shoemaker's papers on the genus it is a relatively simple matter to sort out the previous confusion in the New Zealand species. Crawford (1937) established that there were in the British Museum specimens of C. acutum from Auckland, New Zealand; and from “internal evidence” he deduced that various papers in the New Zealand literature (Chilton. 1921; Thomson and Chilton, 1886; Thomson, 1880) referred to C. acherusicum. Specimens of the latter from Lyttelton Harbour were also found in the British Museum. C. sextonae is a new record from New Zealand.
Under Corophium crassicorne Chilton had included C. contractum and, with a slight query, C. bonellii. In fact, none of these are in his material and it seems almost certain that Chilton's mis-identification was due to the fact that he had been sent specimens of C. acherusicum from Holland labelled C. crassicorne. These specimens, to which Crawford draws attention, are in the Chilton collection. In attempting to rationalise the differences between these specimens and the previous figures and descriptions of these and other species by overseas workers, Chilton concluded that the species varied extensively and that there was only one species known from New Zealand. This readiness to accept wide variability within species without further questioning is unfortunately responsible for many of the now obvious errors in his work.
Corophium sextonae Crawford, 1937 (emend.). (Figs. 1–21.)
Crawford, 1937. 620–623, fig. 3A-H; 4G-H.
[Footnote] *(This basic dichotomy on the attachment of the uropods is often not obvious in mounted specimens but the difference between ventral attachment and insertion in notches in the lateral margin is immediately obvious in mounted specimens. Uropod 2 is also attached ventrally or in notches but not so strikingly and it is much more difficult to convey this difference accurately in drawings.)