COPEPODA 



95 



Description. f<j>. Size of specimen from Thor St. 183 4-05 mm.; anterior division 3-13 mm., 

 tvrosome 0-92 mm. Sars' specimens measured 4-8111111., Wolfenden's specimens 4-65 mm. and Far- 

 ran 's specimens measured 3-9 — 4-5. 



The shape of the body is practically as figured by Sars, except for the distinctly longer lateral 

 spines of the thorax, which are directed downwards and backwards. The rostrum is not undivided 

 as stated by Sars, but is, as shown in fig. 7 a (PI. II), distinctly bifurcate terminally. On each side of 

 the vulva a somewhat triangular plate was found, and a short receptaculum seminis was observed 

 (fig. 7 b) ; the structure of the genital apparatus was rather complicated, but was not examined in the 

 details; figs 7 b— c will give an impres- 

 sion of its structure. The furcal rami 

 are 1-4 as long as wide, and a little 

 shorter than the anal somite. 



The ci7itenmdae do not reach 

 to the end of the anal somite, but only 

 somewhat beyond the end of the geni- 

 tal somite. The segment 2 is ri as 

 long as 8 oj 9, which is scarcely ri as 

 long as segment 13, and 1*2 shorter 

 than segment 20; segment 19 is a little 

 longer than 20 and 22 which are of 

 almost equal length, and longer than 

 segment 2. The appendages differ from 

 those of G. tenuispinus by the presence 

 of a Sp. in segment 13. 



The antennae have the Re 

 about 1/5 as long as Ri, but are scarcely 

 different in other respects. The maxil- 

 lulae differ from those of G. teniiispinns 

 by Iyi 3, which only bears 4 setae in 

 addition to the sensory lobe, and by the Re III, which possesses 6 Sa + * Sp. The maxillae (fig. 7 d) 

 have the exterior margin less strongly convex than the preceding species; the Sp. 2 of the first lobe is 

 three times as long as the lobe itself, and the Sp. of lobe IV is stronger as well as longer than the 

 corresponding Sp of lobe V. The maxillipes differs from those of the preceding species by a rounded 

 lamelli-form protuberance on the exterior surface of the second basipodite (fig. 1 a). The articulation 

 between the Re I— II of the first pair of legs is better developed than in G. tenuispinus (text-fig. 24 b), 

 and so is the articulation between Ri I — II of the second pair of legs (text-fig. 24 c), the St. of pes II 

 has only 19 teeth; along the inner margin of the second basipodite of the fourth pair of legs distally 

 and posteriorly one to two rows of broad stiff bristles were observed (fig. 1 c). 



The oral surface of the labrum has a well developed longitudinal series of hairs, which 

 are, however, only indistinctly divided into the usual 5 groups as seen in fig. 7 f ; group III is 



Text-fig. 24. Gaidhis brevispinus G. O. Sars. 

 a. f 9. Head from the left with parasite attached to maxilla X 18. b. f<?. 

 Pes I sin. in ant. view X 80. c. Pes II sin. Ri in ant. view X 80. d. fcf. 

 Rostrum X 57- e. ftf. Abdomen X 33- f- fcf- X 9- g- YQ. (Stage V) X 33- 

 h. YQ. Abdomen lateral view X 33- i- y9- Pes H R i i n ant . view X 80. 



