44 



MEDUSAE OF THE WORLD. 



bell, and 2 large principal tentacles of the budding medusa. In H. prolifer, on the other hand, 

 the medusae are usually set free with but one well-developed tentacle. The bell of H. pulcher 

 may become asymmetrical in later life ( ?) The hydrorhiza is thin and branching. There is a 

 flexible collar-like pensarc at the base of the hydranth. Medusas are developed upon stolons 

 from the hydranth above the circlet of long tentacles. When set free the medusa is 1.5 to 2 mm. 

 high, of symmetrical form. 5 longitudinal lines of nematocysts extend up the sides of the 

 bell to the apex. 3 small tentacle-bulbs. 2 equally well-developed tentacles arise side by 

 side, from the base of one of the radial-canals. Entoderm of manubrium and tentacles red. 

 Found off Iceland. I believe this form is probably identical with H. prolifer. 



Genus MICROCAMPANA Fewkes, 1889. 



Microcampana, FEWKES, 1889, Amer. Naturalist, vol. 32, p. 595; Bull. Essex Inst., Salem, vol. 21, No. 7, p. in. 



The type-species is Microcampana conica Fewkes, from Santa Cruz Island, off the coast 

 of California. 



GENERIC CHARACTERS. 



Anthomedusae with 6 radial-canals, and 6 radially placed marginal tentacles. One of 

 these tentacles is well developed, and the other 5 are rudimentary. 



It is possible that the vaguely described Rhabdoon singulare, of Keferstein und Ehlers, 

 (1861, Zoolog. Beitrage, p. 86, taf. 13, figs. 6, 7), from Messina, Mediterranean, is a form 

 of Microcampana, but there are apparently 12 longitudinal lines of nettling cells over the 

 exumbrella, and it is uncertain whether there are 4 or 6 radial-canals. The bell is 1.5 mm. 

 high and oval with uniformly thin walls. It is possibly an abnormal medusa of P elella. 



Microcampana conica Fewkes. 



Microcampana conica, FEWKES, 1889, Bull. Essex Inst., Salem, vol. 21, No. 7, p. in, plate 4, 

 fig. 8; American Naturalist, vol. 32, p. 595, fig. 



Size ( ?) Bell conical with a well-developed, elongate, conical 

 apex; slightly asymmetrical. Exumbrella smooth, without meridional 

 rows of nematocysts. 6 marginal tentacles, 60 apart. 5 of these 

 are rudimentary, but the sixth is club-shaped, and about half as long 

 as the bell-height. 6 straight, narrow radial-canals and a ring-canal. 

 Manubrium conical to spindle-shaped, about as long as the depth of 

 the bell-cavity. There is a long, slender, straight, axial canal above 

 the stomach. Bell pink, tentacle-bulbs bright-red, manubrium yellow. 

 Found off Santa Cruz Island, California; under the cliffs of Punta 

 Diablo. 



Genus DICODONIUM Haeckel, 1879, sens. ampl. 



Dieodonium+Dinema s HAECKEL, 1879, Syst. der Medusen, pp. 27, 28. 



A T orc Dinema, VAN BEN ED EN, 1867, Mem. Acad.Roy.des Sci.Belgique, 10111.36, art. 2, pp. 127, 130. 



Dicodonium, VANHOFFEN, 1891, Zool. Anzeiger, Bd. 14, p. 443. 



Sarsiella, HARTLAUB, 1907, Nordisches Plankton, Nr. 12, p. 66. 



The type-species of this genus is DicoJonium cornutum Haeckel, 1879, of the Red Sea. 

 Dinema Van Beneden is a medusa which arises by budding from a Perigotiirnus-\\ke hydroid 

 and therefore belongs to the Tiannae. We use the term Dicodonium in the sense proposed 

 by Vanhoffen, 1891. 



GENERIC CHARACTERS. 



Codonidae with 2 well-developed and 2 rudimentary tentacles. No meridional lines of 

 nettle-cells upon the exumbrella. An apical projection to the bell and an axial canal pro- 

 jecting upward from the stomach, may or may not be present. 



Some of the so-called "species" of Dicodonium are probably only abnormal specimens 

 of Sarsia with 2 tentacles instead of the normal 4. 



FIG. II. Microcampana 

 after Fewkes in Amer- 

 ican Naturalist. 



