8 G. O. Sårs. [No. 4 



Pl. I, figs. 1, 2, 3). The finer details of its structure are rather 

 difficult to make out in preserved specimens, owing to the destruc- 

 tive action of the alcohol. 



The anterior antennæ (Pl. II, fig. 1) are built upon the very 

 same type as in Acartia, being of nearly uniform thickness through- 

 out, and exhibiting a peculiar nodular appearance. They are some- 

 what shorter than the anterior division of the body, and consist 

 each of apparently 17 articulations, some of which, however, are 

 only faintly indicated. The articulations carry setæ of very various 

 lengths and pointing in different directions, most of them being finely 

 ciliated. None of the articulations are produced in front to denti- 

 form projections. 



The posterior antennæ (fig. 2), as in Acartia, are very delicate 

 in structure, with the inner ramus considerably elongated and imper- 

 fectly defined from the basal part. The Ist joint of the latter car- 

 ries a strong curved seta in front. The proximal joint of the inner 

 ramus has, in the middle of the anterior edge, a dense row of about 

 8 finely ciliated setæ gradually increasing in length distally; and a 

 similar seta is attached to the end of the joint in front. The ter- 

 minal joint is very slender and is scarcely expanded distally. 

 Along the obliquely truncated and slightly bilobed end, are attached 

 numerous slender setæ, some of which are almost as long as the 

 whole antenna. The outer ramus is scarcely Va the length of the 

 inner, and is apparently composed of 5 articulations, the Ist of which 

 is more than twice as long as all the others combined. It carries 

 in all 7 setæ, none of which are particularly elongated. 



The anterior lip (see Pl. I, fig. 3, Pl. II, figs. 3, 5) is rather 

 large and is trilobate at the end, the middle lobe being quadrangular 

 in form and very prominent (see Pl. I, fig. 3). 



The posterior lip (see Pl. II, fig. 5) is much smaller and is bi- 

 lobate, each lobe being produced at the outer corner in an incurved 

 ciliated lappet. 



The mandibles (fig. 6) are powerfully developed, with the body 

 thick and vaulted, appearing, in the dorsal aspect of the animal 

 (Pl. I, fig. 1), as 2 rounded lateral prominences. The masticatory 

 part is strongly inflexed and securiformly dilated, with the cutting 

 edge divided into numerous sharp teeth, the outermost of which is 

 much stronger than the others. The palp is of considerable size, 

 with the basal part oblong in form, and carrying 2 densely plumous 

 setæ outside. The inner ramus is imperfectly biarticulate, the 



