152 



64. Acartia discaudata, Giesbrecht. 



(PL CII). 



Dias discaudatus, Giesbrecbt, Die freilebenden Copepoden der Kieler Fohrde. 7t.e Bericht. d. 

 Commiss. Unters. Deutsch. Meere, p. 148, PL IIT, figs. 4, 22, 23; PL V, fig. 18; PL VI, fig. 17; 



PL VIII, figs. 32, 33; PL IX, fig. 30. 



Specific Characters. Female. Anterior division of body of a form similar 

 to that in the 2 preceding species. Front without any tentacular filaments. La- 

 teral lobes of last segment of metasome rounded off and quite smooth. Urosome 

 likewise without any traces of spinules or denticles, and rather robust, genital 

 segment very large, conspicuously dilated in its proximal part, and very pro- 

 tuberant below in the middle; 2nd segment terminating dorsally in a rounded 

 protuberance; 3rd segment flattened and considerably expanded distally. Caudal 

 rami of rather an unusual appearance, being bulbously dilated, and rounded oval 

 in form, with the marginal setae comparatively short and conspicuously dilated at 

 the base. Anterior antenne about the length of the anterior division of the body, 

 and without any denticles in front. Last pair of legs resembling those in A. 

 Clausi, the terminal joint being spiniform. though somewhat less strong than in 

 that species. 



Male resembling that of the 2 preceding species, though perhaps less 

 slender. Urosome of normal appearance, the caudal rami not, as in the female, 

 bulbously dilated, but of a similar form to that in the male of A. Clausi. Last 

 pair of legs considerably larger than in either of the 2 preceding species, right 

 leg much elongated, being more than twice as long as the left, with the lamellar 

 expansions inside the 3 first joints comparatively small, terminal joint rather 

 narrow, almost claw-like. 



Colour. Body of female semipellucid, with a distinct bluish grey hue ; 

 that of male paler. 



Length of adult female 1.20 mm., of male 1.10 mm. 



Remarks. This form may at once be distinguished from the other known 

 species, at any rate in the female sex, by the peculiar structure of the urosome, 

 but more especially by the greatly dilated caudal rami. The male differs less 

 conspicuously, though the last pair of legs exhibit well marked peculiarities. 

 Another distinguishing character not mentioned in the above diagnosis, is the 

 large size and peculiar sac-like form of the spermatophore often found attached 

 to the genital segment of the female. 



