COPEPODA 



221 



The rostrum has the basal portion long and rather slender, and is divided into two rather short 

 branches, which each possesses a very short tooth; the whole structure is completely like Scott's 

 fig. 4, PL XXVII. The crista is scarcely different from that of the female. The fifth thoracic tergite 

 has near the dorsal margin a distinct slender tooth, almost reaching the middle of the first genital somite. 

 The abdomen (text-fig. 72 a) is like that of the preceding species, but the lateral process of the first genital 

 somite is less prominent. The antennulae as well as the oral appendages are scarcely different from 

 those of S. Thorii (text-fig. 72 b); the natatory legs do not differ from those of the females. The right 

 endopodite of pes V (text-fig. 72 c) is very short, and consists of three segments, which are indistinctly- 

 separated ; the second segment is the longest, and the third one is a short conical process bearing a 

 slender seta. The first outer segment is long, and distinctly widened out terminally, where it medially 

 possesses 3 expansions anteriorly and a single more prominent outer one posteriorly; the second outer 

 segment is comparatively short, and, outwards, 

 convex with a terminal expansion, and the third 

 one is short, rounded, with a single spine. The 

 described terminal parts of the right exopodite 

 form a clasping organ (text-fig. 72 c d). The 

 two cylindric basal segments of the left leg 

 (text-fig. 72 e) have each a basal rounded process 

 as seen in figure; the third basipodite has an 

 inner terminal one as well. The left endopodite 

 consists of two segments, of which the one is 

 rather short and rounded with distal process, 

 while the other has two diverging processes, 

 of which the one is axeshaped. The left exo- 

 podite consists of a short basal segment and 

 a longer distal one, inwards excavated and 

 enlarged towards end; the inner margin of 

 this is terminally and posteriorly densely spinous, 

 and anteriorly a laminous process divided into two spines is found. The third segments consists of a 

 rounded basal portion with a few teeth, and a much longer pointed spinelike portion (PI. VIII figs 

 13 a-b). 



YQ (St. V). Size of female from Thor St. 82 was 3-45 mm.; anterior division 2-80; tiresome 0.65 

 mm. Size of female from St. 90 was 3-54 mm. 



The frontal keel is less prominent than in the adult, though distinct. The lateral corner is 

 produced into a distinct tooth (text-figs 73 a e). The fifth foot of the female is much shorter than in 

 the preceding species; the limitation between the segments is more indistinct, the third outer segment 

 is only represented by a short spine, and the inne* spine is not as long as the three terminal segments 

 (text-figs 73 c d). The fifth foot of the male is characterized by a short, distinct spine in the left exo- 

 podite as well as by the pointed endopodite; the branches of the right side, especially the endopodite, 

 are distinctly more rounded. 



Text-fig. 72. Scottocalanus securifrons Th. Scott f d 1 - 



a. Abdomen X 15- b. Segments VII- XIV of the left antennula 



X 51. c. Pes V dext X 33- A. Pes V dext. Re II-III in right 



view. e. Pes V sin. two first segments in dorsal view. 



