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(G.O. Sars, 1877)

Description
— Generic features. Carapace short and emarginate posteriorly, anterior margin rounded without any definite rostral projection or produced into a very short, obtusely triangular rostrum.
Antennule usually short, with third segment somewhat expanded distally. Antennal scale oval, apex considerably produced; thorn at distal; end of unarmed portion of margin not articulated. Eyes short and thick, with the cornea occupying about half of the total organ; slightly flattened dorso-ventrally.
Tarsus of third-eighth thoracic endopods four-segmented, proximal subsegment of carpo-propodus short, swollen, armed with long setae, cut off from second subsegment by a somewhat oblique articulation. Exopod of fourth male pleopod usually five-segmented, armed distally with two long modified setae which form 'pincers'; fifth pleopod rudimentary as in female. Uropod short.
Telson long and narrow, lateral margins armed with small spines; apex cleft more or less deeply, cleft armed with teeth.
— Species. P. helleri is so similar to Paramysis arenosa that only a brief summary of the principal differences is given.
Antennal peduncle longer than in Paramysis arenosa.
Antennal scale longer and narrower, with the apex relatively less produced than in Paramysis arenosa.
Eyes not so broad and thick as in Paramysis arenosa, yet extending rather more beyond the lateral margin of the carapace.
Thoracic limbs with tarsus of the endopods equal in length to, but more slender than, the merus of the same as in Paramysis arenosa, but with the exopod longer. In both species the third segment from the distal end is the longest.
Telson broader than in Paramysis arenosa and with the cleft more open distally.
Uropods armed with an irregular row of 9-10 spines, which extend from the statocyst for about three-quarters of the length of the endopod. This is a marked difference from Paramysis arenosa, in which the spines extend right to the tip of the margin and are much more numerous.

Colour
The chromatophores are arranged in very much the same pattern as in Paramysis arenosa, but there are none on the maxillular somite.

Size
Length about 11 mm.

Depth range
P. helleri is a littoral form living quite close to the coast in shallow water.

Remarks
The species is euryhaline and eurythermic. It occurs close inshore in several places off the coasts, estuarians etc.

Distribution in the North Sea
Southern North Sea? No exact information. Mediterranean origin

World distribution
Mediterranean; Black Sea; estuarine, coastal.

[After Tattersall and Tattersall, 1951]

Paramysis helleri