10 



[No. 7. 



looking as a pair of slightly flexuous cylindric chords, ascending 

 from the inferior part of the head and joining the eye somewhat 

 posteriorly. Also the ocular muscles are very slender, having 

 their point of affixment close to the inferior face of the head. 



The ocellus has the form of a small black spot, located 

 immediately in front of the slight prominence issuing from the 

 ventral side of the head posteriorly. 



The antennulae (fig. 3), affixed to either side of the above- 

 named prominence, appear at first sight very similar to those or- 

 gans in Latona, On closer examination, they are however found 

 to differ materially by the setiform flagellum being distinctly 

 articulated to the basal part, in front of the bundle of sensory 

 filaments, whereas in Latona the flagellum forms the immediate 

 continuation of that part. It is about three times as long as 

 the basal part, but very slightly curved, not as in Latona geni- 

 culate, and on both edges provided with delicate cilia, the ex- 

 tremity being drawn out to a fine point. 



The antennae (fig. 4) are very powerful organs of locomo- 

 tion, the scape, issuing from each side of the head, being exceed- 

 ingly thick and muscular, with numerous circular folds around 

 its proximal part, indicating its great flexibility in that region. 

 Of the strong muscles moving the scape, the two levatores are 

 very conspicuous; both originate from the dorsal face of the head 

 and converge inferiorly to the base of the scape, the posterior 

 occupying the space between the eye and the heart, the anterior 

 that between the eye and the optic ganglion. At the extremity 

 of the scape, between the insertion of the two branches, a strong 

 spine is affixed to the inner side, and from the outer side, some- 

 what nearer the base, a much more delicate setiform appendage 

 arises. The branches, as in the other Sididae, are very dissi- 

 milar both as to size and structure, the upper being by far the 

 larger and more abundantly supplied with natatory setae. This 

 branch is somewhat compressed and composed of but two joints, 

 the outer slightly longer but considerably narrower than the inner. 

 The latter is quite simple, without any trace of the large seti- 

 ferous dilatation of the inner edge distinguishing the genus U- 



