288 THE SCHIZOPODA. 



Remarks. — The reference of this larva to E. distinguenda H. J. H. is certain, 

 because I have a nearly complete series of the following stages of development 

 and growth up to the adult specimens. The larvae of the stage described are 

 distinguished from those of other species by the combination of possessing a 

 slender body, a high and anteriorly steep dorsal keel and somewhat long eye- 

 stalks. A comparison between the larvae just described with the corresponding 

 stage described and figured by Sars as belonging to E. pellucida (" Challenger " 

 Rept., pi. 29, fig. 7 and pi. 30, fig. 40) is not without interest. In certain respects 

 Sars's larva is more, in other features less, developed than the larva of E. dis- 

 tinguenda; E. pellucida has the second pair of thoracic legs considerably longer 

 than E. distinguenda, and the last j^air of pleopods with both rami setiferous, 

 while the telson has still seven terminal spines and the antennular flagella are a 

 little less developed than in E. distinguenda. — Similar cases of differences in 

 the development between various species of the genus Euphausia have been 

 pointed out in my paper on the Schizopoda of the Belgian Antarctic Expedition. 



Nyctiphanes simplex H. J. Hansen. 

 Plate 12, figs. 3a-3f. 



A. Intermediate F urcilia-Stage (figs. 3a-3d). — The frontal plate (fig. 3b) 

 very large, somewhat less than twice as broad as long, longitudinally concave 

 and anteriorly cut off, with the front margin about half as long as the basal 

 breadth of the plate and conspicuously concave but not angular at the middle; 

 the antero-lateral angles feebly produced, acute. — The carapace has a well- 

 developed tooth on the lateral margin, while the usual dorsal keel is very short 

 and low, placed a little farther from the end of the frontal plate than from the 

 posterior margin. 



The eyes are extremely large with moderately long stalks. — The antennulae 

 are very thick; the process from first peduncular joint reaches beyond the middle 

 of the third; second and third joints slightly longer than broad; the upper 

 flagellum thick, nearly conical, unjointed and a little longer than the lower. — 

 Antennae with the rami subsimilar in shape, but the exopod a little shorter than 

 the endopod. — Maxillipeds (mxp.) with the exopod a Uttle shorter than the 

 endopod. — First pair of thoracic legs scarcely as long as the maxillipeds, with a 

 rudimentary exopod and a small two-branched gill; the endopod has one dis- 

 tinct and two indistinct articulations. Second pair half as long as the first, 

 with a rudimentary ])ranchia; third pair quite rudimentary. 



First and second pairs of pleopods with the exopod well developed, seti- 



