AGLAURA. 117 



Station 4574 ; surface ; 1 specimen, with only five radial canals. 



Station 4681 ; 300 fathoms to surface ; 1 very fragmentary specimen. 



Station 4707 ; surface ; 1 specimen, 35 mm. in diameter. 



Station 4740 ; 300 fathoms to surface ; 1 specimen, 40 mm. in diameter. 



All of these specimens have seven blind canals per octant, and the 

 gonads are lanceolate in outline. A surface form, from the warm regions 

 of all oceans. 



Trachynemidae Gegenbaur, 1856. 



(Including Aglauridae Haeckel.) 



Trachomedusae with eight radial canals ; without blind centripetal canals ; 

 with numerous tentacles, of either one or two kinds, but arranged in a 

 single series ; with or without gelatinous peduncle ; gonads either linear 

 or pendent. 



Some confusion has been caused to students of this family by the diver- 

 gent views and accounts which have been published of the genera Penta- 

 chogon and Homoeonema, both of which were originally described by Maas 

 ('93) from the collections of the "Plankton " expedition. Later studies of 

 the same author (: 05, : 06 b ) demonstrated that the species which he united 

 under Homoeonema belong to two different families, and that since the type 

 species, H. plaiygonon, is a halicreid, the name Homoeonema must be removed 

 to the Halicreasidae. This left the remaining species without any generic 

 name; to remedy this deficiency Maas (:06 b ) has proposed Isonema. Unfor- 

 tunately this name is already preoccupied by a genus of Mollusca, so that 

 the generic name Arctapodema proposed by Dall (: 07) must be used, if the 

 two species in question, Homoeonema amplum Maas and H. macrogmter Van- 

 hbffen, are to be separated generically from Pentachagon, as both Maas and 

 Vanhoffen believe is necessary. 



Aglaura Peron et Lesueur, 1809. 



An examination of considerable series of this genus from the Atlantic 

 as well as from the Pacific has convinced me that my former grouping of 

 the species (: 04, p. 257) was erroneous, and that Maas and Vanhdffen are 

 no doubt correct in maintaining that neither the form of the gonads nor 

 the length of the peduncle, which I believed to characterize A. octagona, 

 are of any taxonomic significance in this genus. Vanhdffen (: 02 b ) main- 



