LEPTOMEDUS.E. 



9 



WILLSIA, Forbes, 1846. 



Similar to ProbosciJactyla, but with six or more primary radial-canals. The hydroid 

 belongs to the genus Lar Gosse. 



Order 2. LEPTOMEDUSjE Haeckel, 1886. 



Hydromedusae with gonads upon the radial-canals. When present the otoliths are of 

 ectodermal origin. The medusae arise through alternation of generations from Campanu- 

 larian hydroids. 



Family No. i, THAUMANTIAD^). 



Leptomedusae without lithocysts. 



Subfamily No. i, MELICERTIN^. 



With simple, unbranched radial-canals and an equal number of lips, without oral ten- 

 tacles. Cirri or marginal clubs may or may not be present. 



THAUMANTIAS, Eschscholtz, \%29 = Tetrtinfmti + T/iiiii>tiiinti(is, Haeckel, 1879. 



Four or more tentacles. Four radial-canals. No marginal clubs or cirri. Hydroid: 

 T haumantias. 



LAODICEA, Lesson, i$4$ = Octonema + Laodice, Haeckel, 1879. 



Four or more tentacles. Four radial-canals, with marginal clubs or cirri. Hydroid: 

 Cuspidella. 



MELICERTUM, Oken, 1815; sensu L. Agassiz, i%ta=Melicertella+Melicertum, Haeckel, 1879. 

 With eight or more tentacles. Eight radial-canals. No marginal clubs or cirri. Hydroid: 

 Melicerturn Agassiz. 



M.ELlCER.TlSSA = Mclicertissa + MflicfrtiJnitn, Haeckel, 1879. 



Similar to Melicertum, but with marginal clubs or cirri between the tentacles. 



ORCHISTOMA, Haeckel, 1879. 



More than eight radial-canals. With or without marginal clubs or cirri. 



TIMOIDES, H. B. Bigelow, 1904. 



Four radial-canals. The ring-canal gives rise to blindly-ending centripetal diverticula. 

 Numerous tentacles and cirri. Four gonads on the four radial-canals. Stomach 

 mounted upon a peduncle. 



Subfamily No. 2, POLYORCHIN.E. 



The radial-canals give rise to branches which end blinJlv and do not connect with the 

 marginal ring-canal. 



STAURODISCUS, Haeckel, 1879. 



With four radial-canals, each of which gives rise to two side branches, which end blindly. 



PTYCHOGENA, A. Agassiz, 1862, 1865. 



With four radial-canals which give rise to numerous blindly-ending side branches. Gonads 

 leaf-shaped and developed upon the side branches of the radial-canals. 



POLYORCHIS, A. Agassiz, 1862 to 1865. 



With four radial-canals which give rise to numerous blindly-ending side branches. 

 Numerous sac-like, sausage-shaped gonads attached to the radial-canals and to 

 their side branches. Ring-canal simple. Bell-margin not cleft into lappets. 



SPIROCODON, Haeckel, lS^g = Goniomeam/rus, Kirkpatrick, 1903. 



Similar to Polyorchis, but the ring-canal gives rise to blindly-ending, centripetal branches, 

 and bell-margin is cleft into lappets. 



