(G.O. Sars, 1864)
Description
— Generic features. Carapace with anterior margin either broadly rounded or produced forward into a very short, obtusely triangular rostrum.
Antennal scale oval with distal spine and naked outer margin.
Proximal subsegment of carpo-propodus not swollen, longer than the succeeding sub-segment and separated from the second by a transverse articulation. Endopod of the first thoracic limb with lobes from second, third and fourth segments well developed; no nail. Thoracic limbs 3-8 with tarsus 5-11-segmented, the first of which is the longest and marked by transverse articulation. Pleopods of the male, first and second pairs rudimentary; third pair biramous, with both exopod and endopod short, tapering and unsegmented; fourth pair with exopod composed of five to six elements of the type usually found in the tribe; endopod very small, two-segmented; fifth pair rudimentary as in the female. Telson deeply cleft and exopod of uropod setose all round.
— Species. Body larger and considerably more robust than in Schistomysis spiritus, with the anterior region of the cephalothorax of about the same width as the anterior somites of the abdomen.
Carapace very short; anterior margin more transverse than in S. spiritus, and somewhat convex on either side of the very short, rounded rostrum, cervical sulcus well marked.
Antennal peduncle moderately long and robust; outer flagellum more than twice as long as the inner.
Antennal peduncle long and slender, second segment the longest.
Antennal scale with outer margin short and unarmed, terminating in a strong tooth beyond which the apex extends for nearly half the total length of the scale.
Eyes large and short, only slightly longer than broad, and only extending slightly beyond the lateral margins of the carapace; cornea large, occupying nearly one-half of the whole organ.
Thoracic limbs with endopods of the third to the eighth thoracic limbs slender, carpopropodus longer than the merus, divided into five to six subsegments, of which the first is the longest; dactylus extremely small; nail setiferous.
Pleopods of the male, third pair biramous, rather larger than in the genus Paramysis, exopod very slender and shorter than endopod. Fourth pair with the endopod very small, two-segmented, sympod long and slender. Fifth pair rudimentary as in the female.
Telson longer than the last abdominal somite, very similar to that of S. spiritus, but with the cleft deeper and much narrower.
Uropods long and slender, endopod tapering and straight, about two-thirds as long as the exopod; inner margin armed with an even row of about sixteen spines which extend from the statocyst to the tip of the endopod. The fourteen proximal spines are equidistant from each other and terminate about two-thirds of the length to the apex, the next spine is a little distance away, and the terminal spine is situated very near the apex of the uropod.
Colour
The whole of the body and abdomen is a pale rosy pink with arborescent brown markings which may be very faint or so marked as to make the animal appear quite brown, according to the state of expansion of the chromatophore.
Size
Length 19 mm.
Depth range
Hyperbenthic. 30-150 m; most common in depth 40-95 m, but it has been taken on several occasions at the surface and close inshore in quite shallow waters.
Remarks
This species may be distinguished from S. spiritus by its more robust form and greater breadth at the anterior end; the short, large eyes; the relatively broader antennal scale with its short outer margin and very long apex, the fewer articulations in the carpopropodus of the endopods of the thoracic limbs; the straight, tapering endopods of the uropods and the branching red, brown or yellow chromatophores.
Distribution in the North Sea
All North Sea, Skagerrak, off W Norway, bottom littoral.
World distribution
E North Atlantic; < 26 - 66 N; Baltic; estuarine to slope.
[After Tattersall and Tattersall, 1951]