488 • MB. B. T. BROWNE ON [Mar. 17, 



are of the greatest importance for the identification of the 

 species. 



Pcron and Lesueur (1809) first described two medusce — Oceania 

 JIavidula from Nice [ = Bianaia Jlavidula, Lamarck (1817); Phiali- 

 dium ^/avirfitZitm, Haeekel (1877)], and Oceania pTiosphorica irom 

 the English Channel [ = Dian(ea phosi^horica, Lamarck (1817); 

 Oceania j^^osphoi-ica, Agassiz (1862); PhiaJidium fliosphoricum, 

 Haeckel (1877)]. These Haeckel has given as synonyms of 

 PJiialidium variahile. The original descriptions appear to me to 

 be too vagne for the identification of the species, as the marginal 

 vesicles have been omitted. 



Two other medusae are placed amongst the synonyms by Haeckel 

 viz. Eiicope variahilis, Claus (1864), and Thaumantias huskiana, 

 Gosse (1853). They may belong to the same species, but I perfer 

 to keep them apart until their hydroid forms have been recognized, 

 as Eucope variabilis belongs to the Mediterranean (Trieste), and 

 Thaumantias huskiana to the British Seas. 



Thaumantias Itishiana I consider a distinct species, and refer to 

 it in this paper under the name of Pkialidium hushianum. 



Claus (1864 and 1881) has given an excellent description with 

 iigures of the growth of the medusa Phialiclium (Eucope) variahile. 

 It is quite possible that Qeryonia planaia, Will (1844), from 

 Trieste, Thaumantias duhia, Kolliiiker (1853), from Messina, and 

 Phialidium viridicans, Leuckart (1856), from Nice, may be stages 

 in developmeet of Phialidium variahile (Claus). 



I have recognized as a distinct species Thaumantias cymhaloides. 

 Van Beneden (1861). It possesses only eight marginal vesicles, 

 by which it may be easily distinguished from the other species. 

 I refer again to this species under the name of Phialidium cymha- 

 loideum (Van Beneden). 



I have found another species vi'hich apparently has been mixed 

 up with Phialidium cymhaloideum (Van Beneden). I cannot find a 

 good description of this medusa by which it may be distinctly 

 recognized from the other species. To prevent confusion I propose 

 to call this species Phialidixim temporarium. It is very much like 

 Phialidium ferrugineum, Haeckel (1864), from the Mediterranean. 

 It may be the same species, but I prefer to keep them apart until 

 the hydroid forms of both have been clearly identified. 



According to Ilincks (1868) there are four distinct species of 

 hydroids,viz. Olytiajohnstonii, Alder, Oampanulina acuminata, Alder, 

 C. rejoens, Allman, and G. turrita, Ilincks, which liberate medusas 

 almost identical in form. These, I have but little doubt, will even- 

 tually be proved to be connected with medusae belonging to the 

 genus Phialidium. At present the rearing of these young medusae 

 has not been carried to the stage which is necessary to connect 

 them for a certainty with the free-swimming Phialidium. 



PuiALiDitTM BUSKIANUM, Gosse. (Plate XVI. figs. 6 & 6 a.) , 



During my visit to Plymouth in September 1893 and 1895, 1 



collected many specimens of a medusa in various stages of develop- 



