Norman, 1892
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. Schistomysis parkeri is shorter and much more robust than S. spiritus.
Antennular peduncle short, distal segment broader than long; setose lobe in the male unusually long and arched backwards and inwards at its extremity.
Antennal scale ovate and broad; outer margin naked, straight and terminating in a strong tooth; apex produced beyond this tooth for about one-fifth of the total length of the scale.
Eyes nearly globular, only extending slightly beyond the lateral margins of the carapace.
Thoracic limbs with short endopods and carpopropodus divided into five or six subsegments, eighth thoracic endopod not smaller than those of the preceding limbs.
Telson cleft to about one-fourth of its length; cleft narrower and the spines arming its margins larger and fewer than in S. spiritus.
Uropods very distinctive, with the endopod curved strongly inwards for the distal third of its length, armed on the inner margin with a row of irregular spines which are extremely small at the proximal end of the row, and extend from the statocyst to about two-thirds of the length of the margin. These spines increase in size distally and tend to be arranged in series of large spines with smaller ones between, the distal three spines are very long, twice as long as any other spines in the row. At the distal end of the endopod is a single, long, strong spine.
Size
Length 10 mm.
Depth range
Littoral, to 60 m depth.
Remarks
This species may be recognised at once by the shape and peculiar armature of the endopods of the uropods. There is a slight incurving at the distal end of this endopod in S. spiritus, but it cannot be confused with the very marked curvature in S. parkeri, whilst the form of the spines arming the inner margin, with the long spine at the distal end, is unlike that of any other species of the genus.
The species is a littoral, neritic form and is evidently euryhaline to some extent, as it has been recorded from estuarine waters.
Distribution in the North Sea
No exact information.
World distribution
E North Atlantic: 31-51°N; estuarine, coastal.
[After Tattersall and Tattersall, 1951]