L.M.B.C. MEDUSA. 265 



tentacles at first are unbranched and become branched 

 later in life. The umbrella in all specimens is about as 

 long as broad, in the older specimens the aboral end has 

 a thick mass of tissue. The ex-umbrella is covered with 

 nematocysts. This medusa may easily be identified, as 

 it is the only British medusa with oral tentacles which 

 has sixteen or more tentacles fairly evenly distributed on 

 the margin of the umbrella. The other medusae with 

 oral tentacles have either less than sixteen tentacles, or a 

 large number which are grouped into either four or eight 

 bundles. 



Lizzia blondina, Forbes (9). 



Forbes first described this species from specimens taken 

 in the Sound of Brassay, Shetland, 1845. 



I took some specimens in Port Erin Bay at the 

 beginning of May, 1894. 



It is difficult at first to distinguish this species from 

 the early stages of Margellium octopunctatum. 



The umbrella is somewhat like Margellium octopuncta- 

 tum in shape but smaller in size, usually about 1£ mm. 

 long and 1^ mm. wide. On the margin of the umbrella, 

 in the adult stage, there are three tentacles on each of 

 the four perradial bulbs and only one tentacle on each of 

 the interradial bulbs. The single interradial tentacle is one 

 of the characteristic features of this species. In Margel- 

 lium octopunctatum usually two or three tentacles are 

 present on the interradial bulb. Lizzia blondina has 

 never more than one interradial tentacle on each bulb. 



The tentacle-bulbs have a light yellowish colour, but 

 the tentacles are colourless. 



There are four simple oral tentacles, each terminating 

 in a single cluster of nematocysts. These never have 

 two terminal clusters as in Margellium octopunctatum. 



