. Discovery reports. Discovery (Ship); Scientific expeditions; Ocean; Antarctica; Falkland Islands. LYSIANASSIDAE 75 Remarks. Both in the dorsal profile of pleon segment 4 and the non-projecting epistome this species resembles rossi, but the slender 1st gnathopod and reddish brown eyes at once distinguish it. A single accessory branchia on both segments 5 and 6. Distribution. Coats Land, 161 fathoms; 'Gauss' winter station, 385 m. Genus Pachychelium, Steph. Stephensen, 1925, p. 121. Schellenberg, 1926, p. 296; 1931, p. 18. To help towards a complete definition of this genus, it may be stated t
. Discovery reports. Discovery (Ship); Scientific expeditions; Ocean; Antarctica; Falkland Islands. LYSIANASSIDAE 75 Remarks. Both in the dorsal profile of pleon segment 4 and the non-projecting epistome this species resembles rossi, but the slender 1st gnathopod and reddish brown eyes at once distinguish it. A single accessory branchia on both segments 5 and 6. Distribution. Coats Land, 161 fathoms; 'Gauss' winter station, 385 m. Genus Pachychelium, Steph. Stephensen, 1925, p. 121. Schellenberg, 1926, p. 296; 1931, p. 18. To help towards a complete definition of this genus, it may be stated that the mandible has a non-dentate cutting edge, no molar, and a well-developed palp; maxilla 1 bears 3-4 strong teeth on the outer lobe, one spine seta on the inner lobe, and lacks all trace of a palp. Pachychelium davidis, Steph. (Fig. 32). Stephensen, 1925, p. 121, fig. 35. Schellenberg, 1926, p. 296, fig. 30 {antarcticum). Occurrence: 1. St. 39. South Georgia. One specimen 3-5 mm. 2. St. 58. Falklands. One specimen (? <J) 6 mm. Remarks. I was unable to trace any inner plate of the maxilli- ped such as Schellenberg shows on one side of his fig. 30 a. Uropod 3 is exactly as figured by Stephensen for davidis, the inner ramus not spine-like as in Schellenberg's figure of antarc- ticum Fig. 32. Pachychelium davi- There are z-x feeble crenulations, with setules, on the hind ' ' 0 b. Mandible. margins of side-plates 5-7; Stephensen shows one setule only on side-plate 7. The 1st flagellar joint of antenna 1 is not en- larged or setose as in davidis, but like antarcticum. Branchial lamellae small, ovate, simple. I am of opinion that antarcticum should be regarded as a synonym of davidis, as the shape of the inner ramus of uropod 3 is probably that of the immature form. Cases like this, where the differential features are so minute, are liable to prejudice any discussion of bipolarity. But see Schellenberg, 1931. Should this prove to be the northern species it would be but a
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