no. 2065. THE CRUSTACEA EUPHAUSI ACE A— HANSEN. 95 



Sta. 4762. May 24, 1906. Lat. 53° 46' K; long. 164° 29' W. 2 

 specimens. 



Sta. 5030. September 29, 1906. Lat. 46° 39' 30" N.; long 145° 

 ' 46' E. 300-0 fathoms. 15 specimens. 



Sur. 32. Locality unknown. 3 specimens. 



Remarks. — The dorsal spiniform process on the sixth abdominal seg- 

 ment is always well developed. In the majority of the specimens from 

 the Pacific the fifth abdominal segment has also a dorsal spine which 

 sometimes is proportionately long, sometimes rather short, some- 

 times nearly or completely rudimentary, and in rare cases wanting. 

 In specimens from the Atlantic the fifth segment has generally no 

 dorsal spine, but among the specimens caught at station 1081, off 

 Cape Cod, this segment has in one specimen a very conspicuous, 

 somewhat long, and strong spine, while in a second specimen the 

 spine is rudimentary. 



Of the very remarkable variation of this species a detailed account 

 may be found in my above-named paper. Here (pi. 2) I add some 

 figures, all drawn with the same degree of enlargement, of the anterior 

 legs of specimens taken together in the Woods Hole region. Figure 2a 

 shows the major part of the two anterior right thoracic legs of an 

 adult male measuring 17 mm. It will be observed that the leg of the 

 first pair has the joints figured even slightly shorter and not at all 

 thicker than those of the second leg; but one small difference between 

 the two legs is important: The seventh joint of the first leg is some- 

 what shorter, with considerably shorter and a little stronger setae 

 than that of the second leg, while in specimens of forma Rhoda the 

 seventh joint of the first leg is similar to that of the second leg. Fig- 

 ure 26 shows the same parts of the corresponding left legs of another 

 adult male, 16.5 mm. long. In this specimen the first leg has the 

 fourth joint conspicuously thicker than in the second leg. Further- 

 more, the fifth joint is slightly thickened, a little elongate, conspicu- 

 ously curved, and with the naked proximal part longer than in the 

 second leg; the sixth joint of the first leg is distinctly thicker than 

 that of the second leg; the seventh joint of the first leg is consider- 

 ably shorter and much broader than that of the second leg, only 

 slightly longer than broad and with its setae thicker, somewhat spine- 

 shaped, and much shorter than on the second leg. Figure 2c repre- 

 sents the two distal joints of the first left leg of a large female, 22.5 

 mm. long. The seventh joint is intermediate between those in the two 

 preceding figures. Figure 2d represents the first left leg of an adult 

 female, 19 mm. long. This leg shows the full Tliysanoessa-deyelop- 

 ment. Its fourth joint reaches forward to a little before the end of 

 the second antennular joint, and a comparison between figure 2d and 

 figures 2a-2b shows the great differences in thickness, length, and 

 equipment with setae or spines among legs of the first pair in different 

 degrees of T/^sanoessa-development in adult specimens. Finally, it 



