370 



than the basipodites, constituting in the young about 3/4, but in sexually 

 mature individuals about 1/2 their length. The triangular-oval telson has 

 an obtuse apex and extends to 1/5-1/3 the length of the basipodite of 

 uropods ni. 



Notes: Two forms — compressa and bispinosa — have been identified 

 within the species, which are distinguished by the degree of development 

 of the dorsal denticles on somites Vl-Vll of the pereon and somites I-II 

 of the pleon, the shape and ornamentation of the segments of the pere- 

 opods, and by the relative length of pereopods V and VI. 



Distribution: A bipolar, circum- Antarctic, moderately cold-water 

 species. In the Northern Hemisphere it inhabits cold-water and 

 moderately cold-water regions of the Atlantic Ocean from 76° to 40° N 

 It penetrates farther south in small numbers and is found in the bermuda 

 and Canary Islands and in the Mediterranean Sea. it is not found in 

 the Central Polar Basin. In the northern part of the Pacific Ocean it 

 is reported only from the Yellow and East China seas (identification 

 doubtful), but is absent in farther northern regions. In the Southern 

 Hemisphere it inhabits the entire South Ocean from the coastal pack 

 302 ice to the zone of the Antarctic Convergence. Together with the cold 

 Antarctic currents it also penetrates farther north, where it has been 

 found in Cape Town (37° S) western Australia (18-25° S), 107-108° E), 

 southern coastal areas of Australia (41° S), and in the Pacific oceanic 

 coastal areas of South America (the Juan Fernandez Islands). 



In the Southern hemisphere P. gaudichaudi is one of the numerous 

 species of the Antarctic plankton, forming at places vast concentrations 

 in the surfacial layer of the water, often together with concentrations 

 of Euphausia superba. During the day the main mass of crustaceans 

 remains deeper of 25-50 m, including layers at 100-200 and 200-500 m, 

 but at night the major part of the population ascends to lesser depths, 

 right up to the very surface. Farther north of the Antarctic Convergence 

 it is confined mainly to cold Antarctic intermediate waters. 



6. Parathemisto (Euthemisto) australis (Stebbing, 1888) (Fig. 157) 



Stebbing, 1888: 1417 {Euthemisto); Barnard, 1930: 421; Hurley, 

 1955: 164; Vinogradov, 1962: 27. 



Length of sexually mature specimens 5-10 mm. 



This species is close to P. gaudichaudi and distinguished from it 

 only by some structural details. 



The body is without denticles on the somites of the pereon and the 

 pleon. 



In males the 5th segment of pereopods III is almost trapezoid, highly 

 broadened distally, its width in the distal part 4/5 its length; the 4th 

 and 5th segments are covered along the posterior margin and adjacent 

 surface area with a woolly mass of short tender setae; in females the 



