1S4 MEnrs.E OF THE WORLD. 



one at the end of each terminal branch of the radial-canals. Gonads in 4 interradial ridges on 

 the sides of the stomach. Manubrium with 4 simple lips. A single specimen found by Giinther 

 at a depth of 1,610 fathoms, N. lat. 52 18.1', W. long. 15 53.9'. 



Sibogita Maas, 1904; with 4 principal radial-canals. Centripetal vessels arise from the 

 ring-canal and fuse with the 4 radial-canals. These canals are of various calibers. The 

 tentacles are hollow. The gonads are developed upon the 4 interradial sides of the manu- 

 brium in the form of a double row of transverse ridges in each quadrant. There are 4 

 simple lips. 



S. geometries Maas, 1905 (Craspedoten Medusen der Siboga Expedition, Monog. 10, 

 p. 17, taf. 3, fign. 16-18.) A single specimen was found near the Celebes, Malay Archipelago. 

 S. simulans Bigelow, 1909, from the Eastern Pacific. 



Niobia Mayer, 1900; with 4 main radial-canals, 2 of which bifurcate so that 6 radial- 

 canals reach the circular vessel. The 4 gonads are developed upon the interradial sides of the 

 stomach. The marginal tentacles develop into free-swimming medusae. The only species is 

 N. dendrotentacula of Tortugas, Florida. 



Maas, 1904, is inclined to include the genera Netocertoides and Dichotomia among the 

 Bythotiaridi, but in these genera the gonads extend outward along the radial-canals and there 

 are solid interradial cirrus-like tentacles upon the bell-margin; they appear, therefore, to be 

 Leptomedusae. 



CHARACTERS OF THE TRIBE WILUADI. 



n'ilHad*, FORBES, 1848, British Naked-eyed Medusae, p. 19. AGASSIZ, A., 1865, North Amer. Acal., p. 171. HAECKEL, 1879, 

 Syst. der Medusen, p. I ^6. BROWNE, 1904 Fauna and Geog. Maldive and Laccailive Archipelagoes, vol. 2, Pt. 3, p. 724. 

 MAAS, 1904, Sitzungsber. math.-phys. Klasse kgl. Bayer, Akad. der Wissenschaften, Bd. 34, p. 43; 1905, Craspedoten 

 Medusen Siboga Expedition, p. 19. HARTI.AUB, 1907, Nordisches Plankton, Nr. 12, p. 5. 



Berenicida (sens, restr.), AGASSIZ, L., 1862, Cont. Nat. Hist. U. S., vol. 4, p. 345. 



H\<lt oluriilt, ALLMAN, 1871, Monog. Tubularian Hydroids. DELAGE ET HEROUARD, 1901, Traite de Zool. Concrete, tome 2, 

 Par. 2, Les Coelenteres. 



Dendrostaurinae with 4 or more primary radial-canals which, during the growth of the 

 medusa, give rise to one or more side branches. Stomach with 4 to 6 or more lobes upon the 

 interradial sides of which the gonads are situated. The tentacles are simple and hollow and 

 are situated at the ends of the main radial-canals and their branches. There are clusters of 

 nematocysts upon the exumbrella above the margin between the tentacles, and there is no ring- 

 canal. These last two characters serve to distinguish the- Williadi from the closely allied 

 tribe Bythotiaridi. 



The tentacles are never grouped into clusters, but arise singly from the bell-margin. There 

 are neither cirri nor sensory clubs upon the bell-margin. The successive development of side 

 branches which arise from the main radial-canals is a distinguishing feature of this tribe. 



It has been shown by Hincks. 1872, and Browne, 1896, that the medusa of Wtlhia stellata 

 Forbes develops by alternation of generations from the hydroid Lar sabellaruni of Gosse, 1857. 



Brandt, 1838, and Browne 1904, found that there is no circular canal in Proboscidactyla 

 and Willsia, and in 1904 Browne showed that there is a tube under the clusters of nematocysts 

 of the exumbrella. Isolated nematocysts move along the bell-margin and then enter one of 

 these tubes and stop, and thus a cluster is formed by the accumulation of nematocysts. 



For the Williadi we adopt the classification of Browne and Maas in the sense in which 

 they define the Williadae. Thus: 



Proboscidactyla, BRANDT, 1835. Williadi in which 4 primary radial-canals leave the stomach. 

 Willsiu, FORBES, 1846, with 6 or more primary radial-canals leaving the stomach. The hydroid of //'. 

 stellata is Lor sabellarum. 



It appears from researches of Hincks 1872, Browne 1896, 1904, and Maas 1904, that the 

 Williadi belong among the Anthomedusae and not, as stated by Haeckel, among the Lepto- 

 medusae. For Browne, 1896 (Proc. Zool. Soc. London for 1896, p. 468), demonstrates that 

 the medusa of ft'ilhia stellata Forbes is derived from a hydroid which was first described by 

 Gosse, 1857, under the name of Lar sabellarum. The best description of Lar sabellarum has 

 however, been given by Hincks, 1872 (Ann. and Mag. Nat. Hist., ser. 4, vol. 10, p. 313, plate 

 i ij I. The polypites are of two sorts and arise from a creeping hydrorhiza which is found grow- 



