42 CLEVE, PLANKTON FROM THE INDIAN OCEAN AND THE MALAY ARCHIPELAGO. 



Description of the male. Body. Length (anterior part 0,6, posterior 0,35) 0,9 mm. 

 Anterioi' part 2-jointed; C'e~Th 1 being twice as long as 7Vi 3 and one and a half times 

 as long as broad. Abdonien not jointed, twice as long as broad. Furca half as long as 

 Ah, its brancbes about 7 times longer than broad, parallel and of equal thickness. Sn 

 near the distal end and very small. Si longer than the short and stiff two St. 



Antennce of the ht pair 6-jointed, the 2nd joint longest. 



Antennce of the 2nd pair nearly as in C. rostratus, its interiör margin entire. 



Posterior 'inaxilliped. B 2 with a Si somewhat approximate to the distal end. 

 Terminal claw reaches to the distal part of 5 1. 



Natatory legs of the 1st — 4th pairs. Re S-jointed. 



Longitudinal proportion of the joints: 



' J?e 1. Re 2. Re 3. St. 



Ist pair 7 4 13 29 



2nd pair 7 6 12 22 



3rd pair 7 7 10 2.5 



4th pair 3 2 7 10 



Se of Re O, O, 1. St of the 1st — 3rd p. knife-like, longer than Re 3, with coarsely serrate 

 margin; St of the 4th p. bristle-like. Si oi Re O, 1, 4 on the 1st p.. O, 1, 5 on the 

 2nd — 4th p. Ri 3-jointed, half as long as Re, not developed on the 4th p. Si 1, 1, 5 

 (Ist pair), 1, 2, 4 (2nd pair) or 1, 2, 2 (3rd pair). 



This species is akin to C. rostratus and still more to C. longicaudis. The resom- 

 blance of the males of C. gihlndus and C. longicaudis is so close, that they raay be easily 

 mistaken. 



Corycseus gracilicaudatus Giesbr. MaJe. 



(Pl. IV, fig. 11—15). 



Diagnosis. Abdomen 2-jointed. The genitaJ segment in front with a ventraily 

 curved spine, ^/a as long as the anal-seginent and the furca together. L. 0,75 mm. 



Description of the male. Body. Length (anterior part 0,4, posterior 0,35) 0,75 mm. 

 Til 3 acute, not reaching to the middle of the genital segment. Th 4 short, acute. 

 Abdomen 2-jointed; genital segment with a ventral spine. Furca with parallel branches 

 of equal breadth throughout; branches at least 10 times longer than broad. Of the two 

 St the longest is somewliat shorter than the furca and twice as long as the second, wliich 

 is somewhat shorter than Si. Longitudinal proportion of the abdominal-segments and the 

 furca, compared with that of the nearly related C. anglicus, C. venustus and C. ohtusus. 



Genital-segm. Anal-segm. Furca. 



C. gracilieaudatus 5 3 5 



C. anglicus -5 , 2 2V2 



C. ohtusus . 5 , rV4 2^/2 



C. venustus -') 3 3V2 



Antennce of the 1st pair (j-juinted, the 4th joint the longest, the Gth the shortest. 



