86 



51. Machairopus minutus, G-. 0. Sars, n. sp. 



(PL L). 



Specific Characters. Female. Form of body comparatively short and 

 stout, with the anterior division broad and depressed, the posterior abruptly much 

 narrower. Cephalic segment about the length of the 3 succeeding ones combined, 

 and, seen dorsally, almost crescent-like, being evenly rounded in front and having 

 the lateral corner much expanded. Penultimate segment nearly transversely trun- 

 cated behind. Last segment of metasome very small, but wholly uncovered. Uro- 

 some scarcely attaining half the length of the anterior division, and gradually 

 tapering behind, lateral edges of the segments finely ciliated. Caudal rami about 

 as long as they are broad, and transversely truncated at the tip, innermost but 

 one of the apical setse not nearly attaining twice the length of the urosome. 

 Anterior antennae rather slender and gradually attenuated, 2nd joint but little 

 longer than the 3rd, 4th about half the length of the latter, terminal part half 

 as long as the proximal part, with the last joint shorter than the other 4 com- 

 bined. Posterior antennae with the outer ramus about half the length of the inner, 

 and 4-articulate. First pair of legs of almost exactly the same structure as in the 

 type species. Last pair of legs with the basal joint somewhat lamellar, and pro- 

 duced at the end inside to a conical process carrying 2 plumose setse, terminal 

 joint scarcely longer than the basal one, and of oval form, narrowly truncated 

 at the tip, and provided with 3 apical and one lateral plumose seta. 



Body of whitish colour, with a broad rosy band across the cephalic seg- 

 ment, and another of the same colour across the anterior part of the urosome. 



Length of adult female 0.65 mm. 



Remarks. This is a much smaller species than that originally described 

 by Brady, the length of which is recorded to be almost twice as large (1.30 mm.). 

 In its external appearance this form looks very like some species of the genus 

 Idya, especially I. minor Scott, and at the first sight may be easily confounded 

 with that species. On a closer inspection, however, it is distinguished by the 

 comparatively broader and more depressed anterior division, and by the rather 

 different structure of the anterior antennse. The colour also is rather characteristic. 



Occurrence. I have occasionally found this interesting form in several 

 places on the west coast of Norway, for instance at Aalesund, Christiansund, 

 Haugesund and Kopervik. It is a strictly littoral form, occurring close to the 

 shore among algae. 



Distribution. Polar islands north of Grinnell Land (2nd Fram Expedition). 



