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of the 1st pair of legs. It may, however, at once be distinguished from that 

 species by the very distinctly developed eye, and also by the characteristic form 

 of the genital segment. 



Occurrence. On examining more closely some samples taken last summer 

 at Bukken, in the lower part of the Stavanger Fjord, just below a steep hill, I 

 succeeded in finding several specimens of this small Copepod. Among them was 

 also a male specimen, which exhibited sexual differences from the female quite 

 analogous to those found in the genus Idya. 



Fam. 10. Thalestridae. 



Characters. Body of rather variable form, in some cases much depressed, 

 in others almost cylindrical or even compressed laterally, the 2 chief divisions, 

 however, never being so sharply defined from each other as in the Idyidos. 

 Eye, as a rule, well developed, in some cases of rather complex structure. 

 Anterior antennae not much elongated, and generally composed of 8 or 9 articu- 

 lations; those in male distinctly geniculate. Posterior antennas with the first 2 

 joints imperfectly defined, outer ramus comparatively small. Oral parts on the 

 whole normal; posterior maxillipeds terminating in a more or less strong clawed 

 hand. First pair of legs with both rami, as a rule, prehensile, armed at the tip 

 with unguiform spines. Natatory legs with both rami 3-articulate, the outer one 

 the longer; inner ramus of 2nd pair of legs in male more or less transformed. 

 Last pair of legs foliaceous, not extended laterally, and much larger in female 

 than in male, covering the ovisac more or less entirely. The latter always single. 



Remarks. This is perhaps the most extensive of all the Harpacticoid 

 families, comprising, as it does, even in the restriction here adopted, numerous 

 genera and species. The family to which it bears the closest relationship, is 

 unquestionably that of the Diosaccidce, to be treated of farther on, the chief dist- 

 inction between the two being the duplicity or non-duplicity of the ovisac. 



