a. 0. Sars. [No. 4 



caudal rami are perfectly symmetrical. Finally, the anterior antennæ 

 are comparatively longer than in the Norwegian form, and the 

 right prehensile antenna of the male is not nearly so powerfully 

 developed as in that species. 



Description of the Female. 

 (pl i— ni). 



The length of fully grown specimens slightly exceeds 1 mm. 

 (1.03 mm.), and the size of this form is accordingly intermediate 

 between that of the 2 other known species. 



The general form of the body (see Pl. I, iigs. 1 & 2) is on the 

 whole rather slender, and the integuments, as in the species of the 

 genus Acartia, are very thin and pellucid. The anterior division is 

 composed of 5 rather unequal segments, the Ist of which represents 

 the head, the last the 2 completely coalesced posterior segments of 

 the metasome. Seen from above (fig. 1), this division appears rather 

 narrow, gradually tapering towards the front, which is somewhat 

 obtusely truncated. 



The cephalic segment about equals in length the 3 succeeding 

 segments combined, and is only slightly vaulted above (see fig. 2). 

 The frontal part is narrowly rounded, and carries 2 extremely delicate 

 recurved tentacular filaments below (see also Pl. II, figs. 3 & 4). 

 The lateral edges of this segment appear somewhat incnrved in the 

 middle (see Pl. I, fig. 2), leaving the oral parts quite unobtected. 

 The Ist segment of the metasome is about as long as the 2 suc- 

 ceeding ones combined, and of these last the anterior one is much 

 the shorter. The last segment is deeply emarginated behind in the 

 middle, and projects on each side in a large wing-like expansion 

 of triangular form and terminating in an acute, somewhat exstant 

 corner. 



The urosome is comparatively very short, scarcely exceeding y 4 

 of the length of the anterior division, and is composed of only 3 

 segments, the Ist of which, the genital segment, is about as long 

 as the other 2 combined, and of a rather peculiar form (see fig. 4), 

 being produced on each side to a broad, obliquely backwards-pointing 



