MEDUSA. I. gi 



vessel. About 32 fairly long tentacles. S marginal vesicles, each containing 3- 4 or more concretions Velum well developed. 

 Manubrium, gonads, and tentacular bulbs yellowish or reddish-brown. 



This diagnosis is based on specimens, examined bv me at Plymouth, and it differs in certain regards from that given 

 b\' Mayer. 



The corresponding hydroid is Campanulina reprns Hincks. 



The medusa is common off the coasts of Great Britain and Holland 



Genus Phialidium Leuckart. 

 Phialidium hemisphaericum (Gronovius). 



Plate IV, fig. 14; Plate V, fig. 3. Textfigs. 16 and 17. 

 Alediisa hentisph<prica Gronovius 1760. Observationes de animalciilis . . . Acta Helvetica. \'ol. IV. — p. 35. 

 Thaiiiinnitias Iwiiiispliarica Forbes 1848. Britisli Naked-eyed Medusae. — p. 49. 

 i. J). Phialidiiiiii viiriahile Haeckel 1879. System der Medusen. — p. 186. 



Phialidiitiii tcinporarium Browne 1S96. On British Hydroids and Medusae. — Proceed. Zool. Soc. Lon- 

 don. — p. 489. Plate XVII, figs. 4, 5, 6. 

 — lieiiiisph(Tricii))i Maver 1910. Medusce of the World. — p. 266. 



For further synonymy, see Browne 1896 and Mayer 1910. 



Bell nearh- hemispherical, 20 — 25 mm wide; gelatinous substance thin. Manubrium small, with 

 4 simple lips. 4 slender radial canals. Gonads oval or linear, their length very much varying; they are 

 placed along the radial canals, somewhat nearer to the circular vessel than to the manubrium. 30—58 

 long tentacles with somewhat swollen basal bulbs. Usually 2 marginal vesicles between every succes- 

 sive pair of tentacles, each vesicle containing one concretion. Velum fairly narrow. Stomach, gonads, 

 and tentacular bulbs yellowish-brown or reddish-'brown. 



Among the numerous species of Phialidium described, two species are recorded as occurring in 

 the North-Atlantic area, viz. Pliialidinm lieinisplxFricniii (Gronovius), about 20 mm in diameter, with 

 up to 39 tentacles (according to Browne; as to the Icelandic specimens, see below), usually with 2 

 marginal vesicles between every successive pair of tentacles, and with linear, elongate gonads on the 

 outer halves of the radial canals; and Phialidium buskiainiin (Gosse) Browne, up to 6 mm in diameter, 

 with 20 — 32 tentacles, with one, sometimes 2, marginal vesicles between every successive pair of tent- 

 acles, and with short, oval gonads between the middle of the radial canals and the circular vessel. 



I am ver\' much inclined to think that these two species cannot be kept apart. But the North- 

 Atlantic material at my disposal cannot serve as foundation for a discussion of the matter. The Zoo- 

 logical Museum of Copenhagen possesses, however, a very large material of Phialidium from the 

 Danish waters and, moreover, a great many specimens, which I brought home from Plymouth in 1914. 

 I consider it most convenient, therefore, to postpone a thorough discussion of the variation of Phiali- 

 dium and the question of the limitation of the species, until that material has been further examined. 

 In the present paper I shall restrict myself to give some information concerning the present 



material. 



12* 



