14 



unusual length, otherwise built in a mucli^ similar manner. Natatory legs 

 exactly as in female. Last pair of legs, however, very small, knob-like, each 

 only tipped with a single slender seta. 



Body in both sexes rather pellucid with only a very slight yellow tinge, and 

 provided in some places with a few small pigmentary patches of a darker colour. 



Length of adult female generally about 3 mm., though in some instances 

 reaching 3.70 mm. ; that of male scarcely attaining 2 mm. 



Remarks. The above-described form is unquestionally the same as that 

 recorded by Giesbrecht from the Mediterranean, the identity of both being at 

 once seen by a comparison of the figures here given with those in Giesbrecht's 

 work. It is true that the present form in several respects shows a near 

 relationship to M. longicornis ; but I think that the above given descriptions 

 of these 2 forms will prove them to be in reality specifically distinct. 



Occurrence. Several specimens of this form have been taken by me at 

 different times and in different places on the Norwegian coast, from the 

 Christiania Fjord and northwards to Kval0. Only a single male has, however, 

 as yet come under my notice, all the other specimens were of the female sex. 



Distribution. Mediterranean (Giesbrecht). 



4. Monstrilla clavaia, G. O. Sars, n. sp. 



(PI. VI) 



Specific Characters. Female. Body rather stout and clumsy, being 

 considerably dilated in its anterior part and viewed laterally, of a pronouncedly 

 clavate shape. Cephalic segment very large, occupying rather more than half 

 the length of the body, and having its greatest width about in the middle, 

 dorsal face remarkably vaulted in front. Tail about half the length of the 

 exposed part of the trunk, and on the whole resembling in structure that in 

 the 2 preceding species; ovigerous spines rather produced, being fully 3 times 

 as long as the tail. Caudal rami exceeding somewhat in length the last 2 

 segments combined, and only slightly divergent, each, as in the 2 preceding 

 species, provided with 5 setae, the innermost but one being, however, consider- 

 ably shorter than the others. Eye inconspicuous. Antennae not nearly attaining 

 the length of the cephalic segment, otherwise built in much the same manner 

 as in the 2 preceding species. Oral tubule rather prominent and occurring 

 somewhat behind the middle of the cephalic segment. Natatory legs, as in 

 M. longiremis, armed inside the 2nd basal segment with a single well-marked 

 denticle, terminal joint of outer ramus with a slight indication of a crenulation 



