55 

 3. Gnathia elongata, Kniyer. 



(PI. XXIII, fig. 1.) 

 Anceus elongatus, Kroyer, Nat. Tidsskr. Ny Rsekke, Bd. II, p. 388. 



Specific Characters. Male: Body rather elongated, with the mesosome 

 of nearly uniform breadth throughout, and the median constriction not very much 

 pronounced. Cephalosome of moderate size, rounded quadrangular, with the supra- 

 ocular processes well -defined. Dorsal face of both cephalosome and mesosome 

 very uneven, with irregular depressions, and clothed .-ill over with minute spinules 

 and short hairs. Penultimate pedigerous segment divided dorsally by a narrow 

 longitudinal groove into 2 halves. Metasome comparatively narrow, and scarcely 

 longer than the 2 posterior pedigerous segments combined, epimera small. Eyes 

 well-developed, though not very large. Mandibles comparatively small, with only 

 a very slight notch outside, inner edge obtusely produced in the middle, tip acute, 

 slightly incurved. Pereiopoda with small tubercles inside the outer joints. Ter- 



I 



minal segment of metasome considerably narrowed in its outer part, which is 

 conical in shape. Uropoda with the rami comparatively narrow. Female: Body 

 much broader than in male, with the last 3 pedigerous segments well-defined, and 

 together forming an oblong oval division about 3 times as long as that preceding it. 

 Cephalosome with the frontal part slightly produced and bidentate at the tip. 

 Pleopoda in both sexes with the rami quite smooth forming narrow site-like plates 

 not fitted for swimming, but apparently respiratory in character. Colour of male 

 greyish white, with a light bluish tinge, of female, yellowish, seniipellucid, with 

 scattered brown dots. Length in both sexes 4 mm. 



Remarks. This form was first described by Kroyer from male specimens 

 collected off the Greenland coast, and was subsequently figured in (laimard's great 

 work. The female, however, has hitherto been unknown. Both sexes are easily 

 distinguishable from those of the other Norwegian species. The immature form 

 (Praniza), however, looks very like that of the 2 preceding species. 



Occurrence. Along the whole Finmark coast, this arctic form is not infre- 

 guently met with. In the harbour of Hammerfest especially, 1 have taken it in 

 great abundance at a depth of from 20 to 40 fathoms, both sexes occurring in 

 nearly equal numbers, and in the same place, larva? (the Prani/a-form) were also 

 found rather plentifully. It extends southwards to the Lofoten Islands; farther 

 south, I have never met with it. The adult animal is very sluggish in habit, the 

 structure of the pleopoda, indeed, showing it to be quite unable to swim. The 

 larva?, on the other hand, move through the water with great agility, and most 

 probably, at times, lead a parasitic life on the skin of various fishes. 



