1^96.] BRITISH HXDEOIDS AND MIEDTTS^. 491 



two tentacles, with a single otolith in each. This specimen was 

 taken ofE the Isle of Man. , ■ ' 



Another specimen, taken at Valencia, measured 20 mra. in width 

 and 11 mm. in length, with 39 tentacles. One to three vesicles 

 between every two tentacles, with a single otolith. 

 ; Thirty-nine tentacles is the maximum number which I have 

 counted in one specimen, and I have not seen more than three 

 marginal vesicles between two tentacles. One or two vesicles are 

 ■ usually present between every two tentacles in specimens possessing 

 30 to 35 tentacles, and one to three vesicles in specimens with more 

 than 35 tentalces. The stomach is short, of a yellowish-brown 

 colour ; and mouth with four lips. The generative organs occupy 

 nearly the whole length of the lower oi,' outer half of each radial 

 canal, and terminate very close to the ring-canal. In mature 

 specimens the generative organs hang in folds and are usually of a 

 yellowish-brown colour. I have noticed in some specimens belong- 

 ing to the intermediate stages that the generative organs have a 

 greenish appearance, and occasionally the stomach and tentacles are 

 greenish too. The greenish colour is not due to a green pigment, 

 but to the reflection of light upon the organs. 



Many specimens |taken at Valencia were infested with a species 

 of Cercaria which lives in the mesoglosa. Halcampa usually selected 

 this medusa, and was often seen attached to one of the generative 

 organs, which showed a remarkable decrease in size compared 

 with the others. 



Phialidium otmbaloideum (Van Beneden). (Plate XVII. figs. 1, 

 2, & 2a.) 



Van Beneden first described this medusa in 1866 under the 

 name of Thaumantias cymhaloides. I have changed the specilic 

 name from the Greek to Latin form, in accordance with the rules 

 on nomenclature. This species has no connection whatever with 

 Medusa cymhaloidea, Slabber, and the synonyms connected with it, 

 which Haeckel has placed under the name of Epenthesis cymha- 

 loidea^ 



I first recognized this medusa during my visit to Valencia in 

 1895, and was able to see many stages in development. As it 

 often occurred along with Phialidium temporarium, I was able to 

 compare the different stages. 



Van Beneden has not given a figure of the species, but his 

 description is sufficiently good to recognize without doubt its 

 identity with the medusae taken at Valencia. 



1st Stage. Four tentacles. (Plate XVII. fig. 1.) — Umbrella bell- 

 shaped, about li mm. in length and about 1 mm. in width, with 

 thick walls (thicker than in the corresponding stage of Phialidium 

 temporarium). Four perradial tentacles, fairly long, and four inter- 

 radial tentacle-bulbs. The basal bulbs of the tentacles and the 

 tentacle-bulbs of a yellowish or reddish-brown colour. Eight 

 adradial marginal vesicles, each with two or three otoliths. The 



