1889.] ON SOME FBESHWATEK OSTBACODA AND COPEPODA. 11 



at a considerable distance from the upper, to either side of the 

 labrum, are pediform and much more powerful than the latter, 

 exhibiting a double geniculate bend. At the base there is a 

 rather complicate system of chitinous stripes, partly anastomos- 

 ing with each other and marking off a short basal joint, to which 

 the free part of the antennae is very movably articulated, form- 

 ing with the same a more or less distinct elbowlike flexure; 

 inferiorly this joint bears 2 short bristles. The free part of the 

 antenna is composed of 4 well defined articulations, the first of 

 which is rather large and muscular, pointing generally forwards; 

 it is provided at the end with 2 very long and slender setae, 

 one of which originates form the inner side of the joint and 

 projects in front, whereas the other is attached to the lower 

 edge and points inferiorly. The succeeding joint, forming with 

 the latter an almost right angle, is nearly of the same length, 

 but much narrower, and exhibits posteriorly, somewhat above 

 the middle, a well marked ledge, to which a peculiar short, ba- 

 culiform, biarticulate appendage is attached, evidently represent- 

 ing a sort of sensory apparatus, nearest corresponding in struc- 

 ture with the so-called olfactory setae in other Crustacea. From 

 the infero-posterior corner of this joint, moreover, a rather 

 strong posteriorly curved seta originates, and inside the terminal 

 edge a transverse series of 6 extremely long and slender nata- 

 tory setae occurs, forming a dense, inferiorly pointing fascicle, 

 generally projecting in front of the succeeding joints. Of these 

 setae the foremost is the shortest, whereas the 4 others are 

 subequal and more than twice as long, considerably surpassing 

 the terminal claws of the antenna. The 3rd joint, forming with 

 the 2nd a similar, though less strong geniculate bend, is both 

 shorter and narrower than the latter, and exhibits about in the 

 middle of either edge 2 short bristles placed close together. 

 The extremity of the joint is somewhat obliquely truncated, 

 forming anteriorly an obtuse projection, to which are attached 

 3 strong claws of unequal length. The last joint, finally, is 

 very small and immovably connected with the 3rd, of narrow 

 cylindric form and at the tip armed with 3 similar claws, pro- 



