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Show 488 MR. E. T. B R O W N E O N [Mar. 17 are of the greatest importance for the identification of species. Peron and Lesueur (1809) first described two medusae-Oceania fiavidula from Nice [ = Bianaea fiavidula, Lamarck (1817); Phialidium fiavidulum, Haeckel (1877)], and Oceania phosphorica from the English Channel [ = Diancea phosphorica, Lamarck (1817); Oceania phosphorica, Agassiz (1862); Phialidium phosphoricum Haeckel (1877)]. These Haeckel has given as synonyms of Phialidium variabile. The original descriptions appear to me to be too vague for the identification of the species, as the marginal vesicles have been omitted. Two other medusae are placed amongst the synonyms by Haeckel viz. Eucope variabilis, Claus (1864), and Thaumantias buskiana 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 buskiana to the British Seas. Thaumantias buskiana I consider a distinct species, and refer to it in this paper under the name of Phialidium buskianum. Claus (1864 and 1881) has given an excellent description with figures of the growth of the medusa Phialidium (Eucope) variabile. It is quite possible that Geryonia planata, Will (1844), from Trieste, Thaumantias dubia, Kollioker (1853), from Messina, and Phialidium viridicans, Leuckart (1856), from Nice, may be stages in developmeet of Phialidium variabile (Claus). I have recognized as a distinct species Thaumantias cymbaloides, 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 cymba-loideum (Van Beneden). I have found another species which apparently has been mixed up with Phialidium cymbaloideum (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 Phialidium 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 Hincks (1868) there are four distinct species of hydroids,viz. Clgtia johnstonii, Alder, Campanulinaacuminata, C. repens, Allman, and C. turrita, Hincks, which liberate medusae almost identical in form. These, I have but little doubt, will eventually be proved to be connected with medusae belonging to the genus Phialidium. At present the rearing of these young medusas has not been carried to the stage which is necessarv to connect them for a certainty with the free-swimming Phialidium. PHIALIDIUM BUSKIANUM, Gosse. (Plate XVI. figs. 6 & 6a.) During my visit to Plymouth in September 1893 and 1895,1 collected many specimens of a medusa in various stages of develop- |
