28 THE VOYAGE OF H.M.S. CHALLENGER. 



cell of the axis, on the other hand, is very large, and encloses a prismatic crystalline 

 otolite (fig. 8, ol). The sense-epithelium forming the exodermal covering of the audi- 

 tory clubs is composed of very long, fine auditory cilia, which diverge radially and so 

 form a bundle in whose axis the club is placed (figs. 7, 8, oh). An auditory clasp, also 

 termed a " marginal mantel clasp " or " centripetal urticating streak " (" otoporpa," fig. 

 4, oo; fig. 8, oo), runs from the basis of each auditory club. It is a broad thickened streak 

 of the exodermal epithelium, consisting of a thick accumulation of thread cells and covered 

 with ciliated sense cells. The longitudinal axis of the auditory clasp is a centripetal pro- 

 longation (sometimes straight, sometimes broken) of the longitudinal axis of the auditory 

 clubs ; both lie in the same meridian plane. The auditory clasps of Cunarcha ceginoides 

 are of the same nature as those of Cunoctantha polygonia (System, p. 317, taf. xix. 

 fig. 2). They are shorter and stumpier than in most other Cunathidae, almost triangularly 

 club-shaped, gradually broadened from the thin distal end (at the marginal urticating 

 ring) towards the broad proximal end, and ending there in a thick crescent-shaped 

 urticating swelling similar to that at the insertion of the tentacle (figs. 4, 8, 0})). Like 

 the three auditory clubs of each collar lobe, the auditory clasps belonging to them are very 

 unequal in size, the medial (interradial) two to three times as long and broad as the two 

 lateral (adradial) ; whilst the latter only project slightly above the proximal margin of 

 the annular canal, the former extends till between the two lobe pouches of each lobe 

 (figs. 2, 3, 4, op). 



In Cunarcha ceginoides, as in all other Narcomedusaa, the peculiar " subumbrella " 

 is limited to the concave ventral side of the peripheric umbrella collar, whilst the 

 entire ventral surface of the central umbrella lens is occupied by the broad gastral 

 disk. The circular coronal muscle of the subumbrella consequently forms a broad mus- 

 cular ring, which only lines the concave surface of the four collar lobes ; its upper or 

 proximal line of limitation touches the coronal furrow and the periphery of the stomach, 

 whilst its lower or distal margin is divided from the strong velum by the urticating 

 ring and nerve ring of the actual umbrella margin. 



The velum is of considerable breadth, thick and compact, considerably broader at 

 the four perradial peronial indentations of the umbrella margin than at the four inter- 

 radial points of the collar lobes (fig. 1, 3, v); it is sometimes extended tensely horizontally, 

 and in that case it narrows the entrance to the umbrella cavity so much that only a 

 narrow opening for the passage of the oesophagus remains ; sometimes it projects down- 

 wards like a funnel (fig. 3, v), and sometimes it hangs loosely and vertically from the 

 umbrella margin like a compact multifold curtain. Like the four-lobed umbrella collar, 

 the broad velum as well as its distal process, present a very different appearance 

 according as they are dilated or contracted, and this is also the same with the umbrella 

 uavity, of which they form the wall (comp. figs. 1, 3, 6). The latter usually appears as 

 a narrow annular hollow space, whose internal (axial) wall is formed by the conical basal 



