REPORT ON THE DEEP-SEA MEDUSJE. 127 



umbrella. These eighty coronal lobes constitute the very movable and flexible velarium, 

 which extends to the velar coronal furrow, and was retroverted on the inner side of the 

 umbrella in most of the spirit specimens examined. A marginal layer of the circular 

 muscles is developed on its subumbral surface, so that it serves as an admirable 

 swimming organ, as in many Rhizostomee. 



The lower umbrella surface (subumbrella, PI. XXX. fig. 1) of this Medusa is marked 

 by a very striking peculiarity, which at the first glance distinguishes it not only from 

 all other Cyaneidae but from all other Medusas hitherto known. The subunibrella is 

 divided by two deep coronal furrows, an inner peristom furrow and an outer marginal 

 coronal furrow, into three separate zones, viz., an inner peristom area, a middle tentacle 

 zone, and an outer lobe zone. The central peristom area of the subumbrella (fig. 9) 

 contains the oral cross with its four perraclial limbs, and the four powerful perradial oral 

 curtains hanging from them, as well as the four interradial genitalia, alternating with 

 the latter. The peristomal coronal furrow, which separates the peristom area from the 

 tentacle zone, cuts deeper into the perradii than into the interradii. 



The] intermediary tentacle zone of the subumbrella is bounded by the peristomal 

 coronal furrow from the peristom area on its concave proximal margin, and by the 

 suburnbral velar furrow, from the peripheric lobe zone at its convex distal margin (fig. 1). 

 Its whole extent is traversed by deep radial furrows, in such a manner that numerous 

 thick radial swellings, branched dichotomously towards the periphery, are placed closely 

 beside each other (quadrant, left, below in fig. 1). Numerous long tentacles are scattered 

 everywhere between these radial ribs or swellings, whilst the peripheric lobe zone of the 

 subumbrella, or the velarium of tentacles, and the central peristom area are entirely free 

 from them. On closer examination we can distinguish on the whole forty such thick 

 radial swellings of the subumbral tentacle zone ; a stronger, perfectly straight, unbranched 

 radial rib runs in the eight principal radia, direct to the eight sense clubs, whilst four 

 bunched ribs, or broader, dichotomously branched radial swellings, run between each two 

 such principal ribs from the centre to the peripheric coronal furrow. Of the eight 

 principal ribs (of which two are shown in fig. 1, left below), the four interradial are 

 about one-fourth longer than the four perradial, as the former project further inwards, 

 between the limbs of the oral cross. The four principal ribs are almost linear, rather 

 broader in the middle, quite straight, and unbranched, but divided by a fine traversing 

 principal furrow into two parallel limbs lying close together, so that they really represent 

 double ribs. The four bunched ribs, which occupy the entire space of an octant of the 

 umbrella, between each two principal ribs, form narrow equilateral triangles, whose base 

 line (or the broad distal margin at the velar furrow) is thrice as broad as the truncated 

 point, or the narrower proximal margin, at the peristom furrow. The two medial bunched 

 ribs, on the two sides of the adradial subumbral furrow, are as broad, but rather shorter 

 than the two lateral bunched ribs which lie near the enclosing principal ribs. Each of the 



