82 



MEDUSA OF THE WORLD. 



middle zone of about 10 to 12 long-knobbed tentacles, and a basal (aboral) zone of" about 10 

 to 12 long-knobbed tentacles. Medusa-buds (?) This form closely resembles Tiarella 

 singularis F. E. Schulze, 1876, a small, isolated, attached hydroid found at Trieste. T ' . singu- 

 lans produces medusa at the base of the polypite below the third zone of tentacles. 

 Margelopsis stylostoma was found at Roscoff, northwest coast of France, in June. 



FIG. 39. Hydroid of Margelopsis stylostoma, after Hartlaub, in Nordisches Plankton. 

 FIG. 40. Margelopsis hartlaubii, after Browne, in Bergens Museums Aarbog, 1903. 



Margelopsis hartlaubii Browne. 



Margelopsis hartlaubii, BROWNE, 1903, Bergens Museums Aarbog, No. 4, p. 10, plate i, fig. 2, plate 3, fig. 3. HARTLAUB, 1907, 

 Nordisches Plankton, Nr. 12, p. 92, fig. 89. 



Bell 2 mm. wide, 2 mm. high. Egg-shaped, with thick walls. 8 marginal tentacles, 2 

 upon each radially placed marginal bulb. These tentacles are ringed with nematocysts, and 

 are somewhat shorter than the bell-diameter. No ocelli. 4 narrow radial-canals. Stomach 

 large, conical, with a broad, flat, quadrangular base, without an axial, apical canal. Mouth 

 a simple, round opening. Gonad encircling the stomach. Color (in formalin): Gonads, 

 stomach, and tentacle-bulbs yellowish-brown. Three specimens; coast of Norway, Osterfjord 

 and Herlfjord, from depths of o to 200 fathoms. 



Margelopsis gibbesi Hartlaub. 

 Plate 9, figs. 4-7. 



Ncnwpsis gibbesii, McCfiADY, 1857, Gymn. Charleston Harbor, p. 163, plate 10, figs. 4-7. FRECH, 1898, Lptli.ua pal<eozoica, 

 Theil i, Bd. I, Lfg. 3, p. 565, Stuttgart (compared with the Graptolites as a floating Tubularian). 



Margelopsis gibbesi, HARTLAUB, 1903, Zoolog. Centralbl., Bd. 10, p. 28; 1899, Nachricht. kgl. Gesell. Wissen. math.-phys. 

 Klasse, Gottingen, Jahre 1899, p. 223, fig. 4. 



Bell somewhat higher than a hemisphere, 2.5 mm. high, and walls quite thin and uniform. 

 There are 4 radially situated clusters of marginal tentacles. Each cluster contains 5 or 6 

 tentacles which arise from a large common basal bulb. Tentacles taper regularly from base 

 to tip, but the tip terminates in a knob of nematocysts. There are about 15 rings of nemato- 

 cysts upon the shaft of each tentacle and the entodermal axis of the tentacle is composed 

 of chordate cells resembling those of Obeha. There are 4 straight, narrow radial-canals. 

 Velum well developed. Manubrium wide and flask-shaped, and mouth a simple, round 

 opening without prominent lips, and without oral tentacles. In the female the ova project 

 prominently from the surface of the manubrium. The gonad surrounds the stomach on all 

 sides. The bell of this medusa is highly contractile, often drawing together so as to cause 

 the mouth to project beyond the velar opening. When the bell is relaxed, however, the manu- 

 brium extends but little more than half-way from the inner apex of the bell-cavity to the 

 velar opening. 



