510 



MEDUSAE OF THE WORLD. 



clubs causes a short temporary "paralysis," but pulsation is soon resumed. Severance of 

 the marginal nerve-ring in 8 places, so as to isolate the sense-organs from the tentacles, does 

 not interfere with pulsation. The operation, however, causes the pedalia to bend inwardly 

 by contraction. When the pedalia are cut off the medusa swims unnaturally, being unable 

 to steer itself and turning in circles and somersaults. Removal of the perradial and inter- 

 radial marginal ganglia produces paralysis of the pulsations. 



When young the exumbrella of this medusa is regularly besprinkled with brown-colored, 

 conspicuous clusters of nematocysts. When the bell is 4 mm. high it is pyriform, thin-walled, 

 and the pedalia are merely short, flattened, swollen basal bulbs of the ringed tentacles. The 

 velarium has no velar canals and there are no gastric cirri. The young medusa is abundant 

 in Nassau Harbor, Bahamas, during the summer. 



Carybdea aurifera Mayer. 



CJiarybdea aurifera (young medusa), MAYER, 1900, Bull. Mus. Comp. Zool. at Harvard College, vol. 37, p. 70, plate 25, figs. 81-83. 



A young medusa was described from the Tortugas, Florida, in 1900, but in 1909 a much 

 larger but yet immature specimen was found. In this large specimen the bell is 7 mm. long, 

 5 mm. wide at the velar margin, thin walled, and tapering to a blunt apex. The exumbrella 



is besprinkled by large, wart-like clusters of nettle-cells. The 

 4 pedalia of the tentacles are 2 mm. long and the shafts of 

 t ^ ie tentac l es about the same length. These tentacle-shafts are 

 each ringed by 7 to 9 rings of nematocysts. The 4 rhopalia 

 are set in niches about I mm. above the velar margin. Each 

 club bears I large, median and 4 small, lateral eyes. The 

 velarium is wide, has well-developed, circular muscles and is 

 supported by 4 perradial frenulae. There are 16 main velar 



FIG. 328. Carybdea aurifera, young medusa. From life, by the author, at Tortugas, Florida, July n, 1909. 

 A, side view. B, oral view showing velar canals. C, gastric cirri. D, side view, and inner side of sense-club. 



canals; the 8 adjacent to the frenulse are narrow and simple, but the 8 adjacent to the 

 tentacles are wide and each gives off 3 or 4 finger-like processes. The manubrium is wide, 

 4-sided and nearly half as long as the height of the bell, with 4 simple lips. There are about 

 100 simple, tapering, unbranched gastric cirri. The most characteristic feature of this species 

 is its uniform rich rosin or golden-brown color. It is a rare form and has been taken only 

 twice in ten years in surface tows, in July, at Tortugas, Florida. 



Carybdea alata Reynaud. 



Carybdea alata, REYNAUD, 1830, Lesson's Centurie Zoologique, p. 95, planche 33, fig. I. VANHOFFEN, 1908, Deutsche Sudpolar 

 Expedition, 1901-03, Bd. 10, Zool. 2, p. 34, fign. 3, 4. 



See synoptic table of species of Carybdea. 



Bell 55 mm. high, pyramidal, with a rounded apex and rounded angles. Bell 42 mm. 

 wide at margin and 17 mm. wide at base of rounded apex. The 4 pedalia are each 27 mm. 

 long and 12 mm. wide at widest part. The rhopalia are 13 mm. above bell-margin. When 

 the bell is 55 mm. high there are 6 wide dichotomously forked velar canals in each quadrant 

 between successive pairs of tentacles. In medusae having a bell 60 mm. high, the forking of 

 these canals becomes more complex and quite irregular, no two quadrants being alike. Thus 



