24 



of the tail. The form described by Scott as Thanmalens Thompsoni is quite 

 certainly different from Giesbrecht's species. 



Occurrence. Three specimens only of this species, 2 females and 1 male, 

 have as yet come under my notice. They were taken in as many different 

 localities, viz., Christiansund, Skutesnaes and Riser. 



Distribution. Western part of the Baltic (Moebius). 



11. Cymbasoma longispinosum (Bourne). 



(PI. XIII) 

 Monstrilla longispinow, Bourne, Quart. Journ. Micr. Science, (2), Vol. 30, p. 575, Pi. 37, 



figs. 14, 10. 

 Syn : Thaiim.-'leus longispinostis, Giesbrecht. 



Specific Characters. Female. Body rather slender, with the cephalic 

 segment only very slightly dilated in the middle, and considerably exceeding 

 half the length of the body. Tail very short, not even attaining the length 

 of the 2 preceding segments combined; genital segment about the size of the 

 last trunkal segment and, seen from above, of a very similar subquadrate form 

 its ventral face considerably protuberant; ovigerous spines of quite an extra- 

 ordinary length, attaining in some instances nearly the double length of the 

 body, and confluent at the base for some distance; distal segment much 

 narrower than the proximal one, being conspicuously constricted at the base, 

 and without any trace of a subdivision. Caudal rami very small, scarcely 

 longer than they are broad, and eaeh only provided with 3 thickish setae of 

 equal length. Eye well developed, at least in female. Antennae comparatively 

 short and stout, scarcely exceeding in length V4 of the cephalic segment and, 

 as in the other species of the present genus, only composed of 4 joints, the 

 last of which is about the length of the other 3 combined and gradually 

 narrowed distally, some of its seta? distinctly ramified. Oral tubule occurring 

 far in front, at only at short distance from the frontal part of the head. 

 Natatory legs with the terminal joint of the outer ramus unusually short, 

 scarcely longer than the middle one, and of a rounded form. Last pair 

 of legs provided at the obtusely truncated extremity with 3 plumose setae, 

 the innermost of which is a little shorter than the other 2; inner lobe 

 well defined, triangular, and extending at right angle to the axis of the leg. 



Male somewhat smaller than female and less slender of form, with the 

 cephalic segment comparatively shorter and nearly of equal width throughout. 

 Tail exceeding somewhat half the length of the exposed part of the trunk, 

 and composed of 3 well defined segments, the middle of which is the smallest; 



