HYDROMEDUSAE. 743 



The siphosome in nearly all the specimens is contracted within the hydroecium, but in 

 one specimen it is more expanded, so that the cormidia are more easily seen. The eudoxomes 

 have a spathiform bract, just like Huxley's figure in shape, a siphon and a contracted tentacle. 



Distribution. Pacific Ocean ; East coast of Australia, and the Louisiade Archipelago 

 (Huxley). Indian Ocean; Maldive Is. Minikoi (Gardiner, 3rd Aug. 1899). 



Genus Diphyopsis, Haeckel, 1888. 



Generic Characters. Diphyidae with two angular, slenderly pyramidal nectophores 

 of similar form and subequal size, one placed behind the other. First nectophore with a conical 

 or campanulate hydroecium. Each cormidium with a special nectophore. Bracts pyramidal, 

 conical or spathiform, with a pointed apex. Phyllocyst simple, ovate, without radial canals. 



Diphyopsis campanulifera (Eschscholtz), 1829. 



Diphyes campanulifera, Eschscholtz (1829, p. 137). Diphyopsis compressa, Haeckel (1888, 

 p. 153, PI. XXXIII.). Diphyopsis campanulifera, Chun (1897, p. 26). Diphyopsis campanulifera, 

 Mayer (1900, p. 75, PI. XXVIII.). 



Sexual generation. Ersaea lessonii (Huxley), 1859. Eudoxia lessonii, Huxley (1859, p. 57, 

 PL III.). Ersaea compressa, Haeckel (1888, p. 123, PL XXXIV.). 



There are about a dozen specimens in the collection and all have the anterior and posterior 

 nectophores isolated. 



The shape of the anterior nectophore is like the figure given by Mayer. The teeth round 

 the mouth of the nectosac have nearly a smooth edge, with just a few fine denticulations near 

 the apex. The largest nectophore .measured 13 mm. in length. A few of the specimens have 

 the siphosome well expanded and the cormidia are clearly shown. 



The largest posterior nectophore measured 17 mm. in length, 7 mm. in breadth and 5 mm. 

 in thickness. The teeth of the nectosac are smooth. 



A few specimens of the Eudoxia stage were found. One resembles Huxley's figure of 

 Evdoxia lessonii. 



Distribution. Atlantic Ocean; Tropical and subtropical regions. Australasian Seas; 

 Amboina Is. (Bedot). Indian Ocean ; Minikoi (Gardiner, 3rd Aug. 1899). 



Genus Ahyla, Quoy et Gaimard, 1827. 

 Ahyla trigona, Quoy et Gaimard, 1827. 



Ahyla carina, Haeckel (1888, p. 156, PL XXXV.). Ahyla trigona, Chun (1897, p. 31). 



There is a single anterior nectophore resembling very closely Haeckel's figure (Haeckel, 

 PL XXXV. fig. 5). It differs only in having a slightly flatter apex and the lateral wings 

 project a little further out. The positions of the nectosac, the soraatocyst, and the hydroecium 

 correspond exactly to the position of these organs in Haeckel's figure of Ahyla carina. The 

 posterior nectophore was not found. 



Distribution. Atlantic Ocean, Tropical and subtropical regions. Indian Ocean ; Maldive Is. 

 Miladumadulu (Gardiner). 



