195 



ranius distinctly 3-articulate and longer than the outer, being more or less bent 

 at the end. Natatory legs very slender, with the inner ramus much shorter than 

 the outer and in the 2 anterior pairs 3-articulate, in 4th pair biarticulate ; those 

 in male having the inner ramus in all the pairs, or only in the 2 anterior ones, 

 transformed. Last pair of legs with the distal joint comparatively small, inner 

 expansion of proximal joint more or less prominent, marginal setae of both joints 

 rather coarse, spiniform. 



Remarks. This genus was established as early as the year 1836 by 

 Westwood, to include the well-known fresh-water species, C. staphylinus Jurine. 

 In recent times, several new species have been added, most of them likewise from 

 fresh water; and a subdivision of the original genus into several nearly-allied 

 genera has been carried out by some recent authors. The present genus is there- 

 fore now generally taken in a much more restricted sense than previously. It 

 still comprises several well-defined species, 2 of which belong to the Norwe- 

 gian fauna. 



123. Canthocamptus staphylinus (Jurine). 



(PI. CXXVI & CXXVII). 

 Monoculus staphylinus, Jurine, Historic des Monocles, p. 74, PI. VII, figs. 1 17. 



Syn: Canthocamptiis minutus, Baird (not Glaus). 



Specific Characters. Female. Body moderately slender and slightly con- 

 stricted in the middle. Cephalic segment scarcely longer than the 3 succeeding 

 segments combined; rostrum forming a very small triangular projection between 

 the insertion of the anterior antennae. Urosome a little shorter than the anterior 

 division, and having the segments rather sharply marked off from each other, 

 genital segment exceeding in length the 2 succeeding ones combined, last segment 

 much the smallest and produced at the end on each side in a short dentiform 

 projection, anal opercle rather prominent, semilunar, and armed with a regular 

 row of simple spinules. Caudal rami about the length of the anal segment, being 

 twice as long as they are broad, and of uniform width throughout, the outer one 

 of the 2 middle apical setae comparatively short and very distinctly denticulate, 

 the inner rather elongated, exceeding half the length of the body. Anterior an- 

 tennse comparatively slender and elongated, exceeding in length the cephalic segment, 

 and clothed with rather short setae, terminal part very narrow and about the length 

 of the proximal part. Posterior antennae of moderate size, proximal joint with 2 

 widely separated setae on the anterior edge, distal joint of about the same length, 



