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G.O. Sars, 1870

Description
— Generic features. Statocyst usually present. Pleopods of female reduced, rudimentary; of male variable. Endopod (and exopod) of uropod without spines. Outer margin of antennal scale without setae; ending in terminal tooth. Eyeplate quadrangular with median cleft and with margins serrated in all species of the North Sea. Eyes rudimentary in the form of flat plates without definite stalks. Eyes fused to form a median plate. Telson rounded. Lateral margins of telson and apex armed with a graduated series of spines and a pair of median setae. Marsupium consists, as in the Genus Amblyops, of two well-developed incubatory brood lamellae.
— Species. Body and carapace similar as Pseudomma affine. Eyes as in Pseudomma affine, but the serrations of eyeplate scarcely extending beyond the antero-lateral region.
Antennal scale with apex of antennal scale generally 1/2, but never less than 1/3 of whole scale.
Antennular and antennular peduncle largely similar to Pseudomma affine.
Uropod, exopod and endopod as in Pseudomma affine.
Telson very slightly shorter than the sixth abdominal somite. Lateral margins of telson armed with small spines. One pair of median setae present; with a maximum of 4 apical spines, not spinulated.

Colour
Similar as Pseudomma affine : eyes with pigment diffused without visual elements.

Size
Length of both sexes up to 17 mm.

Depth range
Hyperbenthic; 200-1400 m. Pseudomma roseum is a bottom-living species and is more abundant at the greater depths.

Remarks
Pseudomma roseum can be distinguished from Pseudomma affine by the following:

- eyeplates: in P. roseum the denticulations scarcely extend beyond the antero-lateral angles.
- apex of antennular scale is longer, usually quite half the total length of the scale in P. roseum.
- in P. roseum there are only two pairs of apical spines on the telson. Apex of the telson is more straight and the apex narrower.
- in European waters the body length of adult P. roseum is at least half as large as that of P. affine.

Distribution in the North Sea
West off Norway, Skagerrak

World distribution
N-Atlantic; Arctic 60-69°N; coastal to slope. Largely similar to Pseudomma affine.

[After Tattersall and Tattersall, 1951]

Pseudomma roseum