(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. Carapace with anterior margin produced forward into a very short, obtuse rostral plate of which the lateral margins are convex, and the apex is slightly produced and pointed; antero-lateral angles rounded; emarginate posteriorly, leaving the whole of the last and part of the seventh thoracic somites exposed; cervical sulcus well marked.
Antennal scale short and about twice as long as broad; outer margin unarmed and ending in a strong tooth beyond which the apex extends considerably; length of unarmed portion of margin from one-half to two-thirds of the total length of the scale; apex rounded, setose all round and along the inner margin; a small distal suture present.
Eyes short and thick; somewhat flattened dorso-ventrally, extending only slightly beyond the lateral margins of the carapace and forward to the proximal end of the third segment of the antennular peduncle; cornea occupying about one-half of the whole organ; pigment black.
Thoracic limbs 3-7 with endopods with the carpopropodus shorter than the merus, four-segmented, the first segment very short and swollen, especially on its inner side and armed with long setae; about half as long as the second segment, articulation between first and second segments somewhat oblique; nail small and setiform. Eighth thoracic endopod smaller and shorter than the preceding ones, with the tarsus equal to the merus, and without the nail. First and second pleopods of the male rudimentary as in the female. Third pair biramous with two-segmented sympod, exopod slender and tapering to a rounded point armed with a single seta; endopod longer than exopod, unsegmented, with well-marked setose lobe, and armed with a row of 6-8 plumose setae. Fourth pair with the sympod long and slender, two-segmented; endopod small and two-segmented with the convex outer margin armed with a regular row of plumose setae; setose lobe on the first segment very small. Exopod shorter than in most of the genera of the tribe, six-segmented, the third segment the longest, two distal ones each armed with a long barbed seta, which together form a weak form of pincers. Fifth pair rudimentary, uniramous, unsegmented.
Telson longer and narrower than the last abdominal somite, tapering distally; lateral margins armed with 19-22 small spines on each side; apex deeply cleft for about one-fourth of the total length of the telson, armed with even, closely-set teeth.
Uropods short, endopod only slightly longer than the telson, statocyst small, inner margin armed along the whole of its length with 28-30 spines which are arranged in an irregular row of large spines with small graduated spines between them. The most distal of the spines is situated right at the rounded apex of the endopod; exopod oval, about one-fifth as long again as the endopod.
Colour
Transparent with arborescent yellow and brown and rose markings.
Size
Length 7 mm.
Depth range
Coastal; shallow, to ca. 10 m.
Remarks
May be distinguished from all the other species of the genus, except P. helleri, by the very long apex of the antennal scale, projecting far beyond the terminal tooth of the unarmed outer margin. From P. helleri it may be distinguished by its shorter and more robust form; narrower telson; the presence of a pair of chromatophores on each maxilla and by the armature of the endopods of the uropods.
Distribution in the North Sea
Southern form, may occur in the southern North Sea, no exact information
World distribution
E North Atlantic: 48-57°N; Mediterranean; coastal, shelf.
[After Tattersall and Tattersall, 1951]