258 DIPHYOPSIS MITRA. 



phores, and twenty-four inferior nectophores. I have also had access to a 

 large series from other parts of the Pacific, and from the Atlantic. 



The Eudoxid was taken at Stations 4570, 4571, 4588, 4615, 4617, 4646, 

 4659, 4663, 4676, 4692, 4694, 4696, 4700, and 4707. For the synonymy of 

 this stage, see Chun ('97a) and Lens and Van Riemsdjik, (:08, p. 50). As 

 noted elsewhere (p. 249) the "Ersaea appendiculata" of Agassiz and Mayer 

 (:02, p. 161, pi. 9, fig. 40) belongs to this species. Comparison of Atlantic 

 and Pacific specimens shows no specific difference. 



Diphyopsis dispar is so well known that no account is necessary here. The 

 diagnostic features of the superior nectophore are given in the key (p. 246). 

 So far as my observations on Atlantic and Pacific material go, the inferior necto- 

 phore never shows such prominent serration of its ridges and base as is to be 

 seen in Haeckel's figure ('88b, pi. 33, fig. 4). On the contrary, these regions 

 are entirely smooth in tffe "Albatross" specimens. An interesting feature 

 of the posterior nectophore is, that the lateral flaps which cover the hydroecium 

 remain separate, instead of uniting to form a closed canal. 



Chun ('97b) has already pointed out that the superior nectophore is ex- 

 tremely variable in form. In several of the specimens the groups of appendages 

 were far enough advanced to show both gonophore and special nectophore 

 (Plate 11, fig. 3). It is interesting that in one individual with eight groups, 

 only the oldest bore both buds, the younger ones having only the common bud. 

 This observation illustrates the difficulty of determining from a study of young 

 material, or of specimens with only the younger parts of the stems and append- 

 ages intact, whether any given species belongs to Diphyes or to Diphyopsis. 



Diphyopsis dispar is known from the Mediterranean, from various local- 

 ities in the Tropical Atlantic, from the Gulf Stream (Hargitt, : 05, p. 60) and 

 even as far north as Newfoundland (Bigelow, :09b, p. 316). Its range also 

 includes the Indian Ocean (Quoy and Gaimard, Lesson), the Malaysian region 

 and the Tropical Pacific in general. Its distribution through the warmer 

 waters of all oceans, parallels that of Rhopalonema velatum and of Aglaura hemi- 

 stoma among holoplanktonic Medusae. 



Diphyopsis mltra (Huxlev). 

 Plate 7, fig. 9; Plate 9, fig. 4; Plate 10, figs. 4, 5; Plate 11, fig. (5; Plate 12, fig. .5. 



Diphyes milra Huxley, '59, p. 36, pi. 1, fig. 4. 



Cymbonecics milra Haeckel, '88a, p. 34, '8Sb, p. 133. 



Muggiaea mitra Chun, '92, p. 89. 



Muggiaea kochi (partim. non Will, '44) Schneider, '98, p. 88. 



Diphyes gracilis Bedot, '96, p. 370, pi. 12, fig. 4, 8 (non D. gracilis Gegenbaur, '53). 



Diphyopsis diphyoides Lens and Van Riemsdijk, : 08, p. 51, pi. 8, fig. 65, 66. 



