“Iphimediella cyclogena, n. sp.
Occurrence.—Antarctic: 1. Sta. 194, 2 ♂♂ 34 and 40 mm., 1 ♀ 37 mm. 2. Sta. 316, 2 ♂♂ 36 and 43 mm., 2 ♀♀ 26 and 48 mm. (the larger ovigerous). Types.
Description.--Lateral margin of head produced into an upper sharp point and a lower rounded lobe separated by a narrow notch. Peraeon segment 7 and pleon segments 1-3 each with 2 dorsal processes. Postero-inferior angles of segments 1-4 rounded, of segments 5-7 slightly produced into points. Side-plate 1. oblong, 2, 3 and 4 pointed below, with very faint serrations on lower anterior margins. Anteroinferior angles of the posterior lobes of side-plates 5 and 6 rounded ; postero-inferior angles of 5-7 quadrate. None of the pleon segments dorsally carinate. Posteroinferior angle of segment 1 quadrate, of segment 2 with a small point, of segment 3 with a strong point. The middle of the lateral margins of segments 1 and 2 with small points, of segment 3 with a strong spinous process. Telson not so narrowly incised as in margueritei.
Antenna 1, 1st joint much stouter than following joints, as long as 2nd and 3rd together, 2-3 knobs at base on lower margin, lower apex produced in a long stout spine extending to end of the spines on 2nd joint, with a tooth on its anterior margin near base ; 2nd joint twice length of 3rd, its upper and lower apices produced as spines. Antenna 2 about as long as antenna 1, similar to that of G. pacifica (infra), but the tooth on the ventro-lateral margin of 2nd joint is not apically bifid and its margins are serrulate, upper and lower apices of 4th joint produced as short spines. Mouth-parts in general like those of margueritei. Epistome produced downwards, gibbous proximally. Upper lip feebly incised. Mandible stout at base, tapering to a thin subacute, strongly chitinised apex, secondary cutting plate in left mandible narrow, strongly chitinised, molar a thin transparent fixed triangular projection. Peraeopods 1 and 2, 4th joint not strongly decurrent, hind margins of 4th, 5th and 6th joints with short stout spines set in transverse rows. Peraeopods 3-5 as in margueritei, 4th joints decurrent.
The ♂ does not differ from the ♀ except in the narrower peraeon ; the eye is not appreciably larger.
Remarks.—In the possession of four pairs of dorsal processes this species comes very close to margueritei. In fact the discovery of the form described as microdentata and other varietal forms with truncate and excavate 1st side-plate in the " Terra Nova " collection would justify one in regarding these specimens as margueritei but for the broadly rounded lower angle of the head. This feature is absolutely constant in the specimens at hand, and there is no hint of possible transitional forms. Nor can this species be regarded as the fully -grown adult of margueritei, owing to the constancy of the 1st-3rd side-plates. One would not expect to find these variable in the young and half-grown, and becoming steed in the adult.”
(Barnard, 1930: 349-350)
