664 



MEDTTS.E OF THE WORLD. 



Fie. 411. Diagrammatic representation of the shape and position of 

 the mouth-arms in the Rhizostomata triptera. 



cross-section. The two groups may, however, be maintained apart more for convenience of 

 classification than because of any non-intergrading distinction between them. 



Indeed the chief distinction between them is that in the Rhiwstomata dichotoma the 

 radial muscles are powerfully and the circular muscles weakly developed whereas in the 

 Rhizostomata triptera the reverse is the case, the circular muscles being the more powerful. 

 Another distinction is that in the Rhizostomata dichotoma the axial duct of each mouth- 

 arm simply bifurcates sending a 

 branch to each arm of the V-shaped 

 lower part of the mouth-arm. In the 

 Rhizostomata triptera, however, each 

 axial duct gives off 3 lateral branches 

 which extend downward along the 

 lines of the 3 rows of frilled mouths 

 and usually rejoin the axial duct at 

 the lower end ot the arm. This may 

 be made clearer by saying that in the 

 Rhizostomata triptera the arm is Y- 

 shaped in cross-section, and the axial 

 duct passes down through the middle 

 of the Y while its 3 lateral branches 

 extend down near the 3 ends of the Y. 

 In the Rhizostomata dichotoma, however, a single duct extends down in the angle of the V and 

 sends off 2 branches into the arms of the V (see text-figures 404 and 411). 



The genera are very closely related, being distinguished by the presence or absence of 

 appendages upon the mouth-arms and by the arrangement of the canal-system. A description 

 of the genera follows : 



Catostylus L. AGASSIZ, 1862. Neither clubs, filaments, nor other appendages upon the mouth-arms. The network of 

 canals on the inner side of the ring-canal ends blindly -without connecting with the stomach. 



L\chnorhiza HAECKEL, 1880. Similar to Catost\lus but with filaments, and no clubs upon the mouth-arms. 



Crambtone MAAS, 1903- Similar to Calost\lus but with clubs and filaments upon the mouth-arms. 



\lastigias L. AGASSIZ. Each mouth-arm terminates in a naked club-shaped extremity. Numerous clubs or filaments 

 among the mouths. The network of canals arising from the inner side of the ring-canal connects with the stomach. 



Pseudorhiza VON LFNDENrELD, 1882. Similar to \lastigias, but without lateral clubs or filaments among the mouths. 

 A terminal club present. The canals which arise from the inner side of the ring-canal between the radial-canals 

 end blindly without connecting with the stomach. 



Phyllorhiza L. AGASSIZ, 1862. Mouth-arms with lateral filaments, but without clubs, as in Lychnorhiza. Canal system 

 as in \fasligias. 



Versura HAECKEL, 1880. Mouth-arms with clubs and filaments as in Crambtone. 4 perradial canals arise directly from 

 the stomach, but the 4 interradial canals result from the fusion of a network of vessels which arise from each inter- 

 radial side of the stomach. No ring-canal, but a marginal network of vessels. An outer and an inner zone of ring- 

 muscles with an annular separation between them. 



Lobonema, gen. nov. Marginal lappets of the bell elongated so as to resemble tentacles. Mouth-arm membranes per- 

 forated. Emmbrella covered with papillae. 



Genus CATOSTYLUS L. Agassiz, 1862. 



Catostylus+ To.voclytus + Rhacopilus, AGASSIZ, L., 1862, Cont. Nat. Hist. U. S., vol. 4, pp. 152, 153. 



Crambessa, HAECKEL, 1869, Zeit. fur wissen. Zool., Bd. 19, p. 509. VON LENDENFELD, 1888, Zeit. fiir wissen. Zool., Bd. 47, p. 



231. BROWNE, 1905, Report Pearl Oyster Fisheries, Gulf of Manaar, p. 519. 

 Toxocl\tus+ Crambessa, HAECKEL, 1880, Syst. der Medusen, pp. 585, 619. 

 Crambessa+Loborhiza, VANHOFFEN, 1888, Bibliotheca Zoologica, Bd. I, Heft. 3, pp. 28, 41, 44; 1902, Wissen. Ergeb. Valdiria 



Eiped., Bd. 3, Lfg. i, p. 51. 

 Toxoclytus+ Crambessa+ Loborhiza, MAAS, 1903, Scyphomedusen Siboga Exped., Monog. II, pp. 47, 61, 80, Si. 



The type species is Catostylus mosaicus of Australia, first described as Cephea mosaica 

 by Quoy and Gaimard, 1824. Agassiz designates this as the type of the genus. 



GENERIC CHARACTERS. 



Rhizostomata triptera the mouth-arms of which bear neither clubs, filaments, nor other 

 appendages. 16 radial-canals, 8 rhopalar, and 8 adradial. The rhopalar canals extend to 

 the bell-margin, but the adradial canals end in the ring-canal. On both its inner and outer 

 sides the ring-canal gives off anastomosing vessels which may join with the radial-canals, 

 but which do not connect directly with the central stomach. 



