TRACHYMKDUSiE — RHOPALONEMA. 



381 



egg-shaped gonads on outer two-thirds of the 8 radial-canals. Colorless, iridescent, or sky- 

 blue. Tropical Atlantic, Indian, and Pacific Oceans, and Mediterranean. Not common at 

 the surface, but abundant at a depth of ioo fathoms. The gonads begin to develop when 

 the medusa is 6 to y mm. wide. Vanhoffen, 1902, presents beautiful figures of this medusa. 



Bigelow, 1909, records the capture of 11 specimens at depths between 300 fathoms and 

 the surface, in the Humboldt Current, off the western coast of tropical South America. 



It will never be possible to specifically determine Quoy and Gaimard's D. faneraria, 

 and I therefore believe that confusion will be avoided by dropping this specific name and 

 accepting the name R. ctrruhum of Haeckel and of Maas. (See text-figures 221 to 223.) 



Rhopalonema striatum Maas. 

 Rhopalonema striatum, Maas, 1893, Ergeb. tier Plankton Exped., BJ. 2, K.c, p. 15, taf. 1, figs. 3, 4. 



Bell flat, the shape of a Chinese hat, 4 mm. wide and I mm. high. 16 tentacles: 8 large 

 radial, 8 small interradial. 16 or more lithocysts alternating with the tentacles. 8 wide, spin- 



Fig. 219. — Rhopalonema vclatum, after Agassiz and Mayer, in Mem. Museum of Comp. Zool. at Harvard College. 



Fig. 220. — Rhopalonema polydact\lum, after Haecke!, 1879. 



Fig. 221. — Rhopalonema cozruleum, after Maas, in Hydromedusen Siboga Expedition. 



die-shaped gonads, extending along the middle of inner thirds of the 8 radial-canals. Velum 

 large. Stomach very short. Mouth with 4 simple lips. Bermudas to Sargasso Sea, tropical 

 Atlantic. Described by Maas from preserved specimens. The flat, expanded shape of the bell 

 may be due to unnatural distortion. (See text-figures 224.) 



222. 224. 



Fig. 222. — Rhopalonema cceruleum, after Haeckel, 1879. 



Fig. 223. — " Rhopalonema funerarium" after Vanhoffen, in Tiefsee 



Expedition, Valdivia. 

 Fig. 224. — Rhopalonema striatum, after Maas, in Ergeb. Plankton 



Expedition. Side view above, oral view below. 



