210 



MEDUS.fi OF THE WORLD. 



Our Melicertissa is equivalent to Melicertissa -\-Melicertidium of Haeckel, 1879. Haeckel 

 would restrict Melicertissa to include medusae with only 8 tentacles, while Melicertidium would 

 apply to medusx with more than 8 tentacles. It is probable that Melicertissa as defined by 

 Haeckel is only the young of his Mi-liiertiJiiim. His name Melicertissa precedes that of Mel i- 

 certiJiuin and should therefore designate the genus. 



Melicertissa is closely related to Melici-rttitn, but is distinguished by its rudimentary mar- 

 ginal sense-clubs or cirri which are absent in Melicertutn. 



Melicertissa clavigera Haeckel. 

 Plate 24, figs. 2 and 3. 



Melictriiisa clavigera, HAECKEL, 1879, Syst. der Medusen, p. 135, taf. 8, figs. 8-12. 



( ?) Melicertella panoclo, HAECKEL, Ibid. p. 135 (a damaged specimen without marginal clubs?). 



Bell 7 mm. in diameter, flatter than a hemisphere, with moderately thin walls becoming 

 thinner toward margin. 16 marginal tentacles with long, hollow, tapering basal bulbs and 

 coiled lash-like ends. When contracted these tentacles are each about half as long as the bell- 

 diameter. 8 of the tentacles are radial and 8 interradial. There are 16 sense-clubs (plate 24, 

 fig. 3) midway between the tentacles. There is a well-developed, black, entodermal, cup-like 

 mass of pigment at the base of each tentacle and sense-club, 32 in all. In some specimens 

 one or more of the interradial tentacles are replaced by a marginal sense-club. Haeckel, indeed, 

 describes only 8 radial tentacles and 24 marginal sense-clubs, there being no interradial ten- 

 tacles. His specimens were obtained in the Canary Islands. At Tortugas, Florida, however, 

 we find specimens with interradial tentacles, but which conform in all other respects toHaeckel's 

 medusa. 



106. 



FIG. 106. Melicertissa clavigera, after Haeckel, 1879. 



FII;. 107. Melicertissa malayica, after Maas, in Hydromedusen Siboga Expedition. 



Velum well developed. There are 8 straight, narrow radial-canals and a simple, circular 

 vessel. Stomach about one-fourth as wide as bell-diameter and the 8 radial-canals arise singly 

 from its periphery 45 apart. Stomach flat and entire manubrium short and not over one- 

 third as long as depth of bell-cavity. There are 8 short, simple lips. The gonads are linear, 

 somewhat sinuous, and occupy the middle halves of the radial-canals, not touching the cir- 

 cular canal or edge of stomach. 



Entoderm of stomach, radial and circular canals, and tentacle-bulbs dull yellow in speci- 

 mens from Tortugas, Florida ; the entodermal marginal ocelli black. Haeckel describes the 

 color of the entoderm in the Canary Island specimens as being bronze-colored, brownish, or 

 greenish-yellow. 



Haeckel found this medusa at Lanzerote, Canary Islands, in January, 1867. We found it 

 on the surface at Tortugas, Florida, early in June, 1906. 



The American specimens are interesting, for they show that there is no natural distinc- 

 tion between the genera Melicertissa and Melicertidium of Haeckel. Parts of the bell-rim are 



