13 



a convergent evolution caused by the adaptation to similar conditions of life. 

 It is undoubtedly, like the species of the said genus, a true bottom-form. 



Occurrence. Some few specimens of this remarkable form were picked 

 ip from a bottom sample taken several years ago at Korshavn from a depth 

 of about 60 fathoms, coarse muddy sand. I have not met with it in any other 

 place of the Norwegian coast. 



7. Platycopia pygmaea, G. O. Sars, n. sp. 



(PI. VII, fig. 2). 



Specific Characters. Female. General form of body resembling that 

 of the preceding species, though comparatively less robust. Anterior divi- 

 sion considerably compressed and, viewed dorsally narrow oblong in out- 

 line, with the greatest width scarcely exceeding Vs of the length. Urosome 

 very narrow and nearly attaining half the length of the anterior division. 

 Caudal rami much more elongated than in the type species, being more 

 than 3 times as long as they are broad; seta of outer edge attached near 

 the base of the ramus. Antennae, oral parts, and 1st pair of legs exhibiting 

 a structure very similar to that in the type species. The 4 succeeding pairs 

 of legs likewise built on the very same type, though differing in the inperfect 

 segmentation of the inner ramus, its 2 outer joints being wholly coalesced in 

 the 2nd pair and only slightly indicated in the 3 succeeding pairs. 



Male differing from the female in a very similar manner to that found 

 in the preceding species. Anterior antennae, as in the male of P. perplexa, 

 only composed of 16 joints, the outer 2 of which are rather elongated and 

 narrow. Last pair of legs of a comparatively more compact structure than in 

 the male of the preceding species, with both rami only composed of 2 joints, 

 the outer one armed at the end of the broad, spatulate distal joint with 2 

 large, sabre-like spines, between which a thin hyaline lamella is attached. 



Colour of the living animal not yet ascertained. 



Length of adult female scarcely exceeding 0.60 mm. ; that of male 0.52 mm. 



Remarks. The present form is nearly allied to the type species, but 

 evidently specifically distinct, differing not only in its much inferior size, but 

 also in some of the structural details, as pointed out in the above given diagnosis. 



Occurrence. Only 3 specimens of this form, one female and 2 males, 

 have as yet come under my notice. They were found in a bottom-sample 

 likewise taken at Korshavn, but from somewhat shallower water, viz., about 

 30 fathoms, muddy bottom. 



