REPORT ON THE DEEP-SEA MEDUSAE. 25 



cleft into eight distal lobe pouches occupying the greater part of the collar lobes ; four 

 perradial tentacles longer than the diameter of the umbrella ; twelve auditory clubs 

 (three on each lobe), the middle auditory club twice as large as the two lateral. 

 Horizontal diameter, 4 mm. ; vertical diameter, 2 mm. 



Habitat. — West Coast of Africa. I first observed a living specimen of these species 

 off Lanzerote, one of the Canary Islands, in December 1866, and the figures of Plate IX. 

 and the following description are taken from this specimen. Later I found a specimen 

 in a glycerine preparation of the Challenger expedition, containing the beautiful Phaeo- 

 daria Ccelodendru7ii, south of the Azores, west from the Canary Islands, lat. 32° 41' N., 

 long. 30° 6' W. Depth, 1675 fathoms. This glycerine specimen from the Challenger 

 collection was very imperfectly preserved, but sufficiently preserved to settle its identity 

 with the living specimen found at the Canaries. It is, however, possible (or probable) 

 that this Medusa does not belong to such a great depth, but was captured in shallower 

 water in drawing up the lead. 



The umbrella (PL IX. figs. 1-3) has the form of a flat cap, and is nearly once and a 

 half as broad as high. When the broad velum hangs loose, the aggregate height of the 

 umbrella (including the velum) nearly ecpials the greatest breadth (in the middle of 

 the height). The umbrella is divided into two distinct anatomical portions, the upper 

 " umbrella lens " and the lower " umbrella collar," by a deep horizontal circular furrow of 

 the exumbrella, the coronal furrow (fig. 3, ec). The central umbrella lens or umbrella 

 disk (fig. 3, iv) is simply formed by the gelatinous body of the umbrella, and has the 

 form of a thick biconvex lens with a rounded edge ; its upper surface is covered with the 

 flat exodermal epithelium of the exumbrella, and is somewhat more strongly vaulted 

 than the lower gastral surface, which is covered by the endodermal epithelium of the 

 stomach. The two surfaces are connected by numerous fine, sinuous elastic fibres 

 which traverse the gelatinous substance perpendicularly (fig. 6, uf; fig. 7, uf). The 

 consistence of the gelatinous substance is considerable, resembling that of a soft gelatinous 

 cartilage. The umbrella collar (" umbrella edge " or shortly " collar "), as we shall term 

 the portion of the umbrella lying underneath the insertion of the tentacles, has a very 

 complicate structure as contrasted with the simple lens lying above it. It consists of a 

 corona of four lobes arising from deep radial indentations or incisions of the umbrella 

 margin, the peronial furrows. And these, again, are caused by the four tentacles having 

 left their original position on the umbrella margin and having emigrated a little way 

 into the exumbrella. I consider this peculiar centripetal change of position of the 

 tentacles into the exumbrella, which is probably connected with their partial development 

 into feelers, as the first " true cause " of the manifold and varying transformations, 

 which the umbrella margin and the adjacent organs undergo in all Narcomedusse. 

 Originally the tentacles were placed immediately on the margin of the umbrella as in the 

 other Craspedotse. When they passed upwards into the external surface of the umbrella, 



(ZOOL. CHALL. EXP. PART XII. 1881.) M 4 



