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1. ALga, psora (Lin.). 



(PI. XXIV.) 



Oniocus psora, Linn(5, Fauna svecica. ed. II, 17(51. 



Syn: Mga cmarginata, Leach. 



Specific Characters. — Body rather broad, oval in form, about twice as 

 long as it is broad, with the dorsal face but slightly vaulted, and very smooth and 

 polished; transverse lines of the 4 posterior pedigerous segments indistinct. Ce- 

 phalon with the front slightly produced in the middle. Coxal plates of moderate 

 size. Metasome about half the length of the mesosome, epimera well-developed 

 and pointed. Terminal segment triangular, pointed at the tip, dorsal face smooth. 

 Eyes subreniform, separated in the middle by a distinct, though rather small 

 interspace. Superior antenna? with the first 2 peduncular joints rather broad, 

 the 2nd being produced at the end anteriorly to a hood-liko projection curving 

 over the succeeding joint, flagellum about half the length of the peduncle. In- 

 ferior antenna? nearly twice as long as the superior, with the flagellum somewhat 

 longer than the peduncle. 1st pair of legs with only 2 blunt spines at the end 

 of the meral joint inside, the 2 succeeding pairs with a row of from 7 to 8 si- 

 milar spines on the same joint; the 4 posterior pairs with the outer part densely 

 clothed with short spines. Uropoda with the inner jjlate deeply emarginated 

 near the end, outside, outer plate oblong, with about 12 short spines along the 

 exterior edge. Colour light reddish brown. Length of adult animal reaching 

 to 50 mm. 



Jxemarhs. — This is the species first recorded, and may accordingly be 

 regarded as the type of the genus. It is easily recognizable by the rather broad, 

 oval body, the distinctly separated eyes, and more especially by the form of the 

 terminal segment of the metasome, and the deep emargination occurring on the 

 inner plate of the uropoda, outside the tip. The name cmarginata proposed by 

 Leach, was, indeed, derived from this last character. 



Occurrence. — This species occurs rather frequently along the whole coast 

 of Norway, from the Christiania Fjord to Vadso, being more generally found on 

 the cod, but occasionally also on other kinds of fishes, for instance the haddock, 

 the ling, the halibut and the shark. It is also not infrequently taken up in the 

 dredge, but, as a rule, only young specimens are caught in this manner. 



Distribution. — British Isles (Sp. Bate), Kattegat (Meinert), North Sea 

 (Metzger), Ireland (Edwards), Spitsbergen (Miers), Greenland (Liitken), Atlantic 

 coast, of North America (Harger). 



