Browne — Fauna and Flora of Valencia Harbour ^ Ireland. 721 



Obelia nigra, sp. noy. 



I have found this Medusa common at Yalencia, Plymouth, 

 and Port Erin, in the Isle of Man, hut have not been able to 

 trace it to any described species that I know of. For the time 

 being, until its Hydi'oid has been traced, I propose to call it 

 Obelia nigra, taking the black colour of certain basal bulbs of 

 the tentacles as a specific character, by which it may be dis- 

 tinguished from the other species of the genus. 



Description of an adult specimen : — 



Umbrella slightly cxuwed ; stomach short, with a quadrangular 

 base, and with a small cone-shaped (apical) process in the 

 substance of the umbrella ; mouth with foiu' lips ; eight mar- 

 ginal sense-organs, with a single otolith in each. Tentacles, 

 150-200. The basal bulbs of the tentacles are of two kinds; 

 the majority are colourless, but others, varying in number and 

 position, contain a dark brown or black pigment. There are 

 usually six coloured basal bulbs in each quadrant; they are 

 about twice the size of the coloiuiess bulbs, and are situated on 

 the inner side of the tentacles. The total number varies 

 between 22 and 27. In some specimens, in addition to the 

 completely coloured bulbs, there are bulbs only partly coloiored, 

 with just one or two small patches of colour. In one specimen 

 30 such bulbs were counted, but usually only two or thi'ee 

 are present. They have the appearance of bulbs developing 

 pigment. The gonads are globular in shape, and situated at 

 about two-thirds the length of the radial canals from the 

 stomach, but never on the inner half of the canal. Diameter 

 of the umbrella, 4-5^ mm. 



In 1895, at Yalencia, this species was taken from April 15th 

 till the termination of my visit at the end of May. It became 

 very abundant after May 14th. In a tow-netting made on 

 July 8th by the Misses Delap many specimens were found. 



In 1896, it was present nearly throughout my visit in the 

 summer. Up to August 24th it was by no means common, 

 often very scarce. On August 28th, a great shoal entered the 

 harbour, and over 500 specimens were preserved. They were 

 mostly young specimens, but many adults were present. The 

 shoal, decreasing in size, remained until September 14th, when 

 the Medusa completely disappeared. In the tow -nettings sent 

 by the Misses Delap I found the species again on September 



