22 



side a quite similar notch to that observed in female; copulative appendage 

 divided at the end into 2 comparatively large diverging lobes of a somewhat 

 sausage-shaped form. Caudal rami more pronouncedly clavate than in female, 

 each provided with 4 slender subequal setae attached to the obtusely truncated and 

 distinctly thickened extremity, one of them apparently answering to the small 

 appendicular bristle found in the female. Antennae much more elongate than 

 in female and distinctly 5-articulate, last joint very movably articulated to the 

 preceding one, and terminating in a slender, slightly curved spine. Natatory 

 legs of exactly same structure as in female. Of a 5th pair of legs not the 

 slightest trace is to be detected. 



Body of female, as usual, very transparent in its anterior part, but other- 

 wise exhibiting a light yellowish-grey colour, and tinged in some places with 

 a darker brownish pigment. 



Length of adult female reaching to 2.50 mm., of male to 1.75 mm. 



Remarks. That the present form is identical with that recorded by 

 I. C. Thompson under the name of Cymbasoma rigidum and subsequently 

 more fully described by Scott as Thautnaleus rigidus, appears to me to be 

 beyond any doubt, and I am also of opinion, that several other forms, described 

 under different names, should be referred to that species. Indeed, I have been 

 unable to find any reliable character to distinguish the several forms enumerated 

 above as synonymes, and I am thus led to the conclusion, that they all should 

 be combined into the very same species, for which of course the earliest name 

 ought to be retained. 



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

 different times and in different places, both on the south and west coast of 

 Norway. Most of the specimens collected were of the female sex; but I have 

 also come across a few male specimens, one of which has been subjected to 

 a closer examination and is figured on PI. X. 



Distribution. Atlantic Ocean off Teneriffe (Thompson). Mediterranean 

 (Giesbrecht), coast of Normandie (Claparede), British Isles (Thompson, Scott), 

 Eastern part of North Sea (Timm). 



