STYLOCHEIHON. 273 



but the three large processes show some differences. The terminal process is 

 thickened at the base, but this thicker part does not, as in N. hoopia, constitute 

 a nearly right angle with the following more slender portion; furthermore the 

 distal, expanded part is only half of the entire process, thus proportionately 

 shorter but broader, more expanded, than in N. boopis, with the inner margin 

 nearly straight and the long terminal margin somewhat incised at the middle 

 and raised on the posterior side (fig. Ih); from the outer side (fig. li) this raised 

 part is seen to be the terminal portion bent strongly backwards and forming 

 a right angle with the p6sterior surface. The proximal process has its distal 

 half regularly and semicircularly curved with the very short terminal part a 

 little expanded and bent considerably forwards as a minute triangle (fig. Ih). 

 The lateral process is slender and unusuallj^ long (fig. Ig), somewhat sinuate 

 and with the incurved distal part short. 



Length of the largest male 23 mm. 



Remarks. — This species is interesting. In general aspect it is somewhat 

 similar to A^. flexipes, though conspicuously more clumsy, but by the structure 

 of the copulatory organs and the serration on the dorsal side of the telson it is 

 more nearly related to TV. boopis; it differs from both species by the maxillulae 

 which possess a real pseudexopod. 



Distribuiion. — N. sexspinosus seems to be rare but widely distributed. 

 In the enormous amount of material studied from many sources and all oceans 

 I have found but three specimens, all males, viz. two from the East Pacific 

 and the third from the northern temperate Atlantic (Monaco, Sta. 2105). 



STYLOCHEIEON G. O. Sars (1883). 



To Sars's diagnosis of this aberrant genus some additions and corrections 

 may be made. 



The carapace is always without denticles on the lateral margin. 



The antennulae have in the females the second and especially the third 

 peduncular joint slender and long, frequently even extremely long, while in the 

 males these joints, and especially the third, are conspicuously shorter and much 

 or very much thicker; the upper flagellum is shorter than the lower and both 

 flagella consist of 6-10 joints, most of them proportionately long; in the females 

 the joints are slender and round, but in the males the major distal part of each 

 flagellum is in most species conspicuously flattened and frequently expanded, 

 in the upper flagellum depressed, in the lower compressed; the basal joint of 



