224 



COPEPODA 



the number of glandular pores is like that of the second foot. The fourth foot is like Wolfenden's 

 figure, but the armature of the posterior surface of the third outer segment differs in minor details 

 (PI. VII fig. 4 b); the structure of the St. is like that of the second foot (PI. VIII fig. 15 b). The fifth 

 pair of legs (fig. 4c) consists of three segments, bearing a few hairs posteriorly; the terminal segment 

 is rather slender, attenuated, and produced into a rather short terminal spine. 



The lateral outline of the labrum etc. is rather characteristic, as seen in fig. 15 a; a well devel- 

 oped epistoma densely covered with about 40 long setae on each side was found; the la brum proper 

 is densely covered with setae, the arrangement of which is similar to that seen in fig. 5 e, though 

 differing in details; anteriorly a group of rather short setae (about 3 deep) is found; this group is on 

 each side continued into a large group of long setae, placed laterally and posteriorly, extending towards 

 the hinder margin, where groups of shorter setae are found. In the area in front of the mentioned 

 groups a median group of fairly long setae is observed. 



The oral surface of the labrum (fig. 4 d) is rather characteristic. Laterally, in front, an almost 

 transverse row of rather short setae is found; behind this a longitudinal row of setae is observed. In 

 the middle, on each side, 3—4 almost completely fused groups of densely placed, fairly long, setae are 

 found. In the middle, around the median circular spots, areas of short spines or granules are found. 

 The lamina labialis seems to be wanting, but the serrula 6-dentata is well developed (PI. VII fig. 4e); 

 111 front, a median wide and elongated group of fairly long setae is found, as well as a lateral rounded 

 one. Between the serrulae and behind, 2 groups of setae are found. The arrangement of the densely 

 placed hairs on the labial lobes and on the area behind was not studied in details, but shows great 

 similarity to that of O. magnus (fig. 5 e). 



fo*. Size of male was 6-17 mm.; anterior division 4-95 mm.; urosome r22 mm. 



The head is rounded, without any frontal crista or spine (fig. 15 d). The rostrum is strong, with 

 short terminal filaments. The lateral corners are rounded, without any spine (PI. VII fig. 4 f). 



The abdomen is only one fourth as long as the anterior division; along the hinder margin of 

 somites II — IV a marginal serrated seam is found; the fifth abdominal somite is almost rudimentary; the 

 comparative length of the first four abdominal somites and the furcal branches is 8, 20, 15, 10 and 5. 



The antennulac extend to the end of the cepbalo-thorax; the two first segments are inflated 

 and much more powerful than those following ; they contain 24 segments, but the articulation between 

 8^9 and 10 and between 12 and 13 is wanting posteriorly. "iEsthetaskeu" are found in the following 

 numbers, 1 in segment 1, 4 in segment 2, 2 in segments 3— 8 ^9, and a single one in segments 10—19, 

 22 and 25. The mensurements are scarcely different from those of the females. The antennae are like 

 those of the female, while the mandibulae differ from those of the female by the much wider third 

 basipodite with three short setae medially. 



The maxillulae differ from those of the female by the rudimentary setae of the Li I and the 

 two short setae of Li II. The maxillae are very similar to those of O. cristatus (PI. VII fig. 6 c), but 

 the spine of lob. IV is comparatively stronger, being longer, though less powerful, than that of lob. V; 

 the number of the setae is scarcely different from that of the female; the sensory setae of the endo- 

 podite have a rather curious structure, with a more or less prominent, rather short, terminal filament 

 surrounded by short delicate dentations. The maxillipeds are widely different from those of the females, 



