COPEPODA 



237 



Description. f$. Size of female from Thor St. 99 was 5-19 mm.; anterior division 4-15 mm.; 

 urosome 1-04. Farran's specimens measured 4-55-1 mm. 



The shape of the body is in the main like that of X. borealis. The first and fifth somites, but 

 especially the fifth, are well marked in front (text-fig. 77 a); the lateral corners are produced into a small tooth. 



The abdomen, which is one fourth as long as the anterior division, has a slightly produced 

 genital somite, and a distinct receptaculum seminis ; along the hinder margin of somites II IV a striated 

 seam is found ; the comparative length of the first three abdominal somites and the furcal rami is 18, 

 12, 9 and 8. 



The antennulae extend tp the end of the fourth thoracic tergite, and consist of 23 segments; 

 the number of "^Esthetasken" is like that of C. chelifer; a proximal seta was found in segments 12, 14, 

 16 and 18, but not in segments 15 and 17; the posterior seta of segment 24 is placed in the middle 

 of the segment, and extends just to the end of segment 25. Segment 24 is 1-2 as 

 long as 23, and 1-5 as long as 24, which is as long as segment 22. 



The exopodite of the antennae is distinctly longer than the endopodite. 

 The mandibulae are scarcely different from those of X. borealis, while the maxillulae, 

 especially the distal portions, are more long and slender than in X. Greeni as well 

 as borealis; the number, but not the shape, of setae in the maxillulae is as in X. 

 Greeni, but the endopodite has only 9 setae. The maxillae are like Sars' and Far- 

 ran's figures; the lobe V has in addition to 3 setae, of which the two are short 

 and delicate, a serrated and distinctly curved spine, which is longer and stronger 

 than that of the fourth lobe; the endopodite has 7 brush-shaped sensory setae in Text-fig. 77. Xantho- 



, ,.,. ... _.. ..... , . calanus pinguis Farr. 



addition to a vermiform one. The maxilhpcds are somewhat less slender than in g Genital somit 



X. borealis; the sensory seta of the second basipodite is fairly long and brush-shaped; X 18. b. yd" (St. V). 



Abdomen X 18. 

 the comparative length between the main divisions is 65, 73 and 48. 



The first pair of legs is like that of X. borealis, but the Se of Re I extends almost to the end 

 of Re II. The second pair of legs differs from that of X. borealis by finer serration of St; the glan- 

 dular pores are like those of the preceding species. The Si of the second basipodite shows an abnormal 

 structure probably due to traumatism, as it is suddenly narrower and then gradually enlarged, 

 where it is divided into three again subdivided branches. The third and fourth pair of legs, the distal 

 segments of which were wanting, are scarcely different from those of X. borealis. The fiftli pair of 

 legs (PI. VII fig. 2 a) is in main features like Farran's earlier description, and is scarcely different from 

 the figure which Far ran has given of a larger specimen (his PI. IV fig. 18); the anterior surface is 

 smooth, but the posterior surface has, as shown in figure, groups of short spines. 



The lateral outline of the epistoma and labrum is like that of X. Greeni, as seen in figure, 

 and they are not distinctly defined from each other. The epistoma has in front a group of long slender 

 bristles; somewhat in front of the transverse row of bristles along the posterior margin a regular 

 transverse series of fairly long setae is found, and just in front of this a group of irregularly placed 

 bristles is found ; laterally two or three groups of short hairs are found. 



On the oral surface of the labmm (PI. VII fig. 2 b), in front and laterally, two oblique almost 

 parallel wide rows of bristles were observed; in the middle, on each side, 4 more or less fused wide 



