12 



ramus rather produced, being fully twice as long as the middle one, and having 

 the outer edge divided into 4 very distinctly marked crenulations. Last pair of 

 legs rather broad at the base, but having the outer part abruptly narrowed 

 and provided at the obtusely rounded extremity with 3 ciliated setae, the inner- 

 most of which is much smaller than the other 2; inner expansion almost rect- 

 angular and carrying a single, but well developed seta. 



Male considerably smaller than female and of somewhat shorter and 

 stouter form of the body, but exhibiting a very similar shape of the cephalic 

 segment. Tail comparatively more slender than in female, and composed of 

 4 well defined segments of nearly equal length, the 1st, as usual, produced 

 below to a club-like copulative appendage terminating in 2 short diverging 

 rami, each armed at the end with a short spine. Caudal rami of a similar shape 

 to that in female, but with one of the apical setae absent. Antennas more strongly 

 built than in female and having the joints more distinctly defined, being more- 

 over conspicuously hinged, the hinge occurring between the last 2 joints. Natatory 

 legs of exactly same structure as i female. Last pair of legs, however, much 

 reduced in size, forming 2 small knob-like prominences issuing from a common 

 base, each prominence tipped by 2 (in some cases only 1) slender setae. 



Body in both sexes of a yellowish grey colour, and on the whole less 

 transparent than in most other species. 



Length of adult female 3.50 mm., of male 2.30 mm. 



Remarks. This species was established in the year 1890 by J. C. Thomp- 

 son, and was only based on a solitary male specimen taken by him off the 

 Puffin Islands. Subsequently, however, Th. Scott recorded this form from many 

 other localities, and has given in the report of the Fishery Board for Scotland 

 (1904) good descriptions and figures of both sexes. He is of opinion 

 that Giesbrecht's species, M. longiremis, is identical with that observed by 

 him; but this is certainly not the case, as will be shown further on. The 

 present species may be easily distinguished from its nearest allies by the some- 

 what robust body and the rather coarse and distinctly granular integuments. 

 Two other characters, both derived from the structure of the natatory 

 legs, may also here be named, viz., the presence inside the 2nd basal seg- 

 ment of 2 well defined denticles, and the very conspicuous crenulation of the 

 outer edge on the terminal joint of the outer ramus. These characters are pretty 

 constant and found quite alike in both sexes. The form recorded by Aurivil- 

 lius under the name of M. intermedia is identical with the present species. 



Occurrence. I have met with this form occasionally in several places, 

 both on the south and west coast of Norway, among other pelagic animals 



