13 



more slender and elongated than in female, with the 3rd joint twice as long 

 as the 2nd and about equal in length to the remaining part of the ramus; 

 inner ramus distinctly 3-articulate, middle joint slender and somewhat arcuate, 

 with 3 subequal setae anteriorly; last joint transformed to a falciform claw ad- 

 mitting of being impinged upon the middle one. Postoral limbs on the whole 

 rather weaker in structure than in female. Copulative appendages comparatively 

 small, each terminating in 3 incurved digitiform processes. 



Body of female only slightly transparent, of a whitish grey colour with 

 a more or less distinct yellowish brown tinge; that in male much more pel- 

 lucid, the shell itself being almost colourless, whereas the enclosed body 

 exhibits in some places a vivid orange hue. 



Length of adult female amounting to 2.60 mm., of male to 2.50 mm. 



Remarks. The present species has by most recent authors been identified 

 with Cypridina brenda of Baird; but it is very questionable if this identifi- 

 cation is correct. Indeed Dr. Skogsberg has found the identification quite inad- 

 missible, and has therefore proposed to retain the specific name given by Lillje- 

 borg to the female sex. In accordance therewith the species is here recorded 

 under the name by which it was distignated by me in the year 1869. It is 

 the type of the genus Philomedes and at the same time of the subfamily 

 Philomedince proposed by Dr. Skogsberg. 



Occurrence. Females of this form are by no means rare of the Norwegian 

 coast in moderate depths on a muddy bottom, and are noted from numerous 

 localities, from the Christiania Fiord up to Finmark. The adult males are much 

 more scarce, and are only quite occasionally captured. The behaviour of the 

 two sexes is very different. Whereas the males are very active animals, swim- 

 ming about with great spead, and in some cases even ascending to the very 

 surface of the sea, the adult females are constantly bound to the bottom, 

 dragging themselves slowly through the loose mud in search of food. This 

 sluggish behaviour is due to the peculiar imperfectness of the natatory setae on 

 the posterior antennae, rendering these limbs quite unserviceable for swimming. I 

 have examined numerous specimens, and have almost constantly found these 

 setae brocken in the very same manner. Only quite exceptionally I have met 

 with one or other specimen with these setae in an intact state, and such 

 specimens had never ova and embryos in the breading cavity, being in all 

 probability still young and virginal. I think that the supposition set forth by 

 G. W. Miiller in this regard is very likely to be accepted, viz., that the above 

 mentioned amputation of the natatory setae is a volontary act of the animal, 

 these setae being only of some use during the short period in which copulation 



