12 G- O. Sars. 



but, excepting the 1st articulation, which has only 2 

 comparatively short setæ, each articulation would seem 

 to give origin to 4 natatory setæ, 2 anteriorly and 2 

 posteriorly, the former being particularly elongated. The 

 last articulation, moreover, has 2 or 3 shorter, spine-like 

 bristles on the tip. During the swimming motions of the 

 animal, the setæ are spread out in such a manner as to 

 form a broad fan, and as they are all finely ciliated, these 

 antennæ may act as most effective propulsive organs. 



The inferior antennæ (fig. 2) are comparatively more 

 strongly built than the superior, and pediform in character. 

 They also consist of a basal and a terminal part, forming 

 together a strong geniculate bend. The basal part, as in 

 the superior antennæ, is bi-articulate, but the distal joint is 

 here much the larger, whereas the proximal one is quite 

 short and less distinctly defined from the body. Both 

 joints are strengthened by several chitinous stripes curved 

 in different directions, and between them is a more movable 

 articulation than between those of the superior antennæ. 

 The proximal joint carries below 2 or 3 short bristles, and 

 from the end of the distal joint issues posteriorly a slender 

 reflexed seta, and anteriorly, somewhat inside the joint, 

 another still longer seta, which curves downwards in front 

 of the terminal part. The latter, which is very movably 

 articulated to the basal part, is composed of only 3 joints. 

 The 1st joint is fully as long as. the distal joint of the 

 basal part, but considerably narrower, and carries at some 

 distance from the base posteriorly a peculiar sensory appen- 

 dage terminating in a very delicate cylindric papilla (fig. 

 2, b). At the end, this joint has posteriorly a single, 

 strong ciliated seta, whereas anteriorly, and somewhat 

 inside the joint, 5 or 6 very slender and elongated setæ issue 



