1896.] BRITISH HYDROIDS AND MEDUS 2. 491 
two tentacles, with a single otolith in each. This specimen was 
taken off the Isle of Man. 
Another specimen, taken at Valencia, measured 20 mm. 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 or 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 mesoglea. 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 CYMBALOIDEUM (Van Beneden). (Plate XVIL. figs.1, 
2, & 24.) 
Van Beneden first described this medusa in 1866 under the 
name of Thawmantias cymbaloides. I have changed the specific 
name from the Greek to Latin form, in accordance with the rules 
on nomenclature. This species has no connection whatever with 
Medusa cymbaloidea, Slabber, and the synonyms connected with it, 
which Haeckel has placed under the name of Epenthesis cymba- 
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 meduse taken at Valencia. 
lst Stage. Four tentacles. (Plate XVII. fig. 1.)\—Umbrella bell- 
shaped, about 14 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. Light 
adradial marginal vesicles, each with two or three otoliths. The 
