Description

provided by NMNH Antarctic Invertebrates

“Rhachotropis antarctica, n.sp.

Occurrence: 1. St. 51. Falklands. 3 ♂♂ 7-10 mm., 6 ♀♀ (2 ovig. 1 with embryos) 7-9 mm.

2. St. 144. South Georgia. 11 ♀♀ (1 ovig. with embryos) 11-13 mm., 2 immat. 8 mm.

3. St. 167. South Orkneys. 2 ♂♂ 10-11 mm., 5 ♀♀ 13-14 mm., 2 immat. ♀♀ 9 and 11 mm. Types.

4. St. 170. South Shetlands. Fourteen specimens, mostly mutilated, incl. ovig. ♀♀, 14-20 mm.

5. St. 175. South Shetlands. 1 ♂18 mm., 19 ♀♀ 16-18 mm., 1 ovig. ♀ 20 mm. Four mutilated specimens.

6. St. 181. Palmer Archipelago. 10 ♀♀ 12-20 mm.

7. St. 182. Palmer Archipelago. 1 ♀ 16 mm.

8. St. 187. Palmer Archipelago. 1 ♂ 11 mm., 1 ovig. ♀ 15 mm.

9. St. 19o. Palmer Archipelago (315 m.). 2 ♂♂ 17 mm., 1 ♀ 15 mm. (somewhat mutilated).

Description. Close to inflata (Sars) but: pleon segments 1-4 tricarinate, all the carinae produced into small acute teeth except the medio-dorsal one on segment 3, and the dorso-lateral ones on segment 4; and telson cleft for not more than, or scarcely more than (St. 51), one-third its length.

Remarks. The much larger size and the fact that pleon segment 4 is tricarinate as well as the preceding three segments distinguishes this species from its northern counterpart inflata. From rostrata (Bonn.) it differs in having dorso-lateral keels on pleon segment 1 as well as on the three following segments, and well-developed eyes.

The smaller specimens from St. 51 do not appear to differ in any way from the others except in the slightly deeper telsonic cleft.”

(Barnard, 1932: 194-195)