RHIZOSTOM^ — TOREUMA. 635 



Rhizostomata Iriplera, continued — 



Crambione Maas, 1903. Similar to Crambtssa, but with both clubs an J filaments upon the mouth-arms. 

 Mailigias L. Acassiz, lSbl= Ma!ligias+ Kiicrambrssa Haf.ckel. Each mouth-arm terminates in a naked club. 

 Numerous clubs or filaments among the mouths. The network of vessels which arises from the inner side 

 of the ring-canal connects with the stomach. 

 Pstudorhisa voN Lendenfeld, 1882. Similar to Mastigias but without lateral clubs or filaments upon the 

 mouth-arms. A terminal club present. The canals which arise from the circular vessel, between the radial- 

 canals end blindly without reaching the stomach. 

 PhyUorhiza L. Agassiz, 1S62. Mouth-arms with lateral filaments, but without clubs as in /.jcAnorAiM. Canal- 

 system as in Mastigias. 

 Vessiira, Haeckel, iSSo. Mouth-arms with clubs and filaments as in Crambione. 4 pcrradial canals arise 

 directly from the stomach, but the 4 interradial canals result from the fusion of a network of vessels which 

 arise from each interradial side of the stomach. An outer and an inner zone of circular muscles with an 

 annular separation between them. 

 Lobonema, gen. nov. Marginal lappets elongated to form tentacles-like organs. Mouth-arm membranes per- 

 orated by window-like openings. Exumbrella covered profusely with papilla:. 

 Rhizostomata lorifera: 8 mouth-arms, very elongate, whip-like, and triangular in cross-section, with frilled mouths 

 developed along the angular edges of the arms (fig. 419, p. 691) The cylindrical upper parts of the arms are rudimen- 

 tary and partially fused one to another by gelatinous arches spanning between them and connecting them with the 

 arm-disk. The genera are as follows: 



Thysaiiostoma L. Agassiz, 1862. No terminal clubs on the mouth-arms. Mouths along the 3 angles through- 

 out length of arms. 

 Lorifera, Haeckel, 1880. Similar to Thysanostoma, but with a naked club at lower end of each arm. 

 Leptobrachia Brandt, l%l% = Leplobrachia + Leonura 'Hayxk.y.i.. Mouths confined to the upper and lower ends 

 of the mouth-arms, leaving the middle part of the arm naked. 

 Rhizostomata scapulata: Each mouth-arm bears a pair of simitar-shaped appendages (scapulcts) which arise from the 

 outer side near the base of the arm and bear frilled mouths (fig. 421, p. 697). The circular muscles of the subumbrella 

 are powerfully, and the radial-muscles weakly, developed, or even absent. The genera are as follows: 



Rhizostoma Cuvier, lSoo=Pilema R^eckel, 1880. 8 free mouth-arms, the lower parts of which are Y-shaped, 

 or 3-winged, in cross-section. Each arm terminates in a naked club. There are no other clubs or filaments. 

 Rhopilema Haeckel, 1880. Similar to Rhizostoma but with numerous clubs or filaments upon the mouth-arms. 

 Eupilema H-aeckel, 18S0. Similar to Rhizostoma, but the arms have neither clubs nor filaments. 

 Stomolophus L. Agassiz, 1S62 =Brachiolophus + Slomolophus, Ha^ck^l, iSSo. The 8 mouth-arms are fused 

 along their sides leaving only the lower ends free and forming an elongate throat-tube for the central mouth 

 which remains open. 

 Rhizostomata simplicia: Rhizostoma: w-ith unbranched mouth-arms. These apocryphal forms are described by Haeckel 

 and by Fewkes from alcoholic specimens of small size. They are apparently immature or injured specimens. No 

 naturalist has seen any of these forms since E'ewkes described hh'^Stomotonemareticulatiim" in 1884. It is probable 

 that we should drop these medusie from further consideration, but in the faint hope that some may be discovered 

 I have given descriptions of them based upon the statements of Haeckel and Fewkes. 



RHIZOSTOMATA PINNATA Vanhbffen. 



Rhizostomata pinnaia, Vanhoffen, 1888, Bibliotheca Zoologica, Bd. i. Heft. 3, p. 40. — Maas, 1903, Scyphomedusen der Siboga 



Exped., Monog. 11, p. 38. 

 Cassiopeidis, Clals, 1883, Organisation und Entwick, Medusen, Leipzig. — von Lendenfeld, 1888, Zeit. fiir wisscn. Zool., Bd. 



47, p. 211. 

 Arcadomyaria, Maas, 1903, Scyphomedusen der Siboga Exped., Monog. 11, p. 88; 1907, Ergeb. Fortschritte der Zool., Bd. i, 



p. 201; 1906, Revue Suisse de Zool., tome 14, p. 100. 



Rhizostomous medusae with 8 linear, pinnately, or complexly branching mouth-arms. 



GENERA. 



Toreuma Haeckel, 1880. 8 rhopalia. 



Cassiopea Peron and Lesueur, 1809. More than 8 rhopalia. 



Genus TOREUMA Haeckel, 1880. 



Toreuma, Haeckel, 1880, Syst. der Medusen, p. 566. — Vanhoffen, 1888, Bibliotheca Zoologica, Bd. i. Heft. 3, p. 40. — Maas, 

 1903, Scyphomedusen, Siboga Exped., Monog. 11, p. 43, 



The type species is Toreuma dieuphila, described by Peron and Lesueur from the Indian 

 Ocean. 



GENERIC CHARACTERS. 



Rhizostomata pinnata with 8 adradial, linear mouth-arms which branch pinnately or 

 complexly, and the main side branches also branch. 8 marginal sense-organs. 



This genus is closely related to Cassiopea and is distinguished only by having 8 rhopalia, 

 whereas Cassiopea has more than 8. Haeckel is the only modern naturalist who has seen 

 any of these forms. They all come from the Indian Ocean. 



