Caehnterata from the Ncrtli Aduitic. 427 



TRACHOMEDUS^. 

 Geryonidae. 



Liriope sp. (?). 



A single young specimen of almost spherical shape, 

 5 millim. in diameter, with four tentacles about 3 millim. 

 long, was taken in a haul from a depth of 1275 fathoms on 

 the 20th of November. 



Aglauridae. 



AgJantha rosea, Forbes. (PI. X. figs. 6-8.) 



By far the most abundant Medusa captured by the 

 'Oceana' was an Aglantha. It was found in hauls from 

 almost all depths, occurring in the greatest numbers in 

 catches made below 1000 fathoms ; but in hauls from between 

 1600 and 1700 fathoms it becomes less frequent. The 

 interior of the bell was often full of Copepoda. 



There is some difficiilty in identifying the species on 

 account of the absence of manubrium, tentacles, sense-organs, 

 and gonads. On the other hand, the eight radial canals, 

 the thimble-shaped muscular umbrella, and the highly charac- 

 teristic cone-shaped summit ("Scheitelaufsatz^') suggest that 

 this Medusa is Aylantha rosea. 



Browne found fully developed A. rosea in April and May 

 in Valencia Harbour. Maas describes A. digitalis from the 

 Plankton Expedition material collected in July in the North 

 Atlantic in the latitude of the Orkneys and Shetlands. It 

 seems possible that fully developed Aglantha may live near 

 the surface during the summer months, but may sink into 

 deeper waters with the advancing season, and may then lose 

 their manubria, tentacles, and other organs. 



A typical ' Oceana ' specimen is shown in fig. 6. Fig. 8 

 represents the margin of the umbrella [u.], from which the 

 velum {v.) has become detached, tearing away with it a 

 number of notch-like depressions (/e.), which afford us some 

 indication of the number (about 80) of tentacles. The tear 

 has occurred along the line of the circular canal. 



The exumbrella is produced into a characteristic cone- 

 shaped summit, which is a highly variable structure. The 

 Aglantha shown in fig. 6 may be regarded as of the normal 

 shape; but in many individuals the cone-shaped summit has 

 dwindled to the condition depicted in fig. 7. In no case, 

 however, did an ' Oceana ' specimen exhibit the other extreme 

 variation described by Maas in A. digitalis, in which the 

 summit was larger than the rest of the bell. 



