714 Proceedings of the Royal Irish Academtj. 



changes its name. This douhle system is useful in cases "vrhere 

 the lledusa has not yet been traced to its Hydroid ; but "when 

 once the connection has been finnly established, in my opinion, 

 the Medusa ought to be called by its Hydroid name, if the 

 latter has priority. My reason for not using the Hydroid name 

 in this case is due to some doubt "^hich I have Mrith regard to 

 the right specific name to be given to the Hydroid. 



It does not come "within the scope of the present Eeport to 

 enter into details concerning the different species of Perigo- 

 nimus; but a revision of the genus is needed. 



Order . — LEPTomnrs^ . 



Agastra caliculata (Hincks). 



Hydroid form. 

 Campanidaria caliculata^ Hincks, 1868, p. 164, pi. xxxi. ; Q-iard, 

 1898. 



Medusoid form. 

 Agastra mira^ Hartlaub, 1897, p. 504, Taf. xxii. 

 Leptomedusa. Gen.? Sp. ? Bro"wne, 1897, P. Z. S., p. 832, 

 pi. xlix. 



Hartlaub fii'st described the free-s"sviinming Medusa under the 

 name of Agastra mira, and his specimens "were obtained off 

 Heligoland in 1895 and 1896, in the autumn. 



At Yalencia, in May, 1895, I found a single specimen of the 

 Medusa, and in August, 1896, three more specimens. These I 

 described and figured in the " Proceedings of the Zoological 

 Society" "without gi"ving a name, as I felt almost certain that 

 these peculiar little Medusae, •without a stomach or tentacles, 

 must have been recently liberated from a Hydroid colony. For 

 this reason I preferred to "wait for the discovery of its Hydroid. 



Portunately there has not been a long delay, as Giard has 

 found the Hydroid Cam'panularia caliculata of Hincks abundant 

 at Wimereux, and has been able to find Medusae in the gono- 

 thecse "which agree "with the description given by Hartlaub of 

 Agastra mira. As Giard points out, the genus Campanularia 

 is con-fined to certain Hydroids which do not possess Medusae, 

 but have simple sporosacs. He has suggested the removal of 

 this species from the genus Campanularia to a ne"w genus, 

 "which he proposes to call Agastra, after the generic name 

 given by Hartlaub to the Medusa. No"w I see no reason 



