5ss 



MEDUSAE OF THE WORLD. 



axial ribs of the mouth-arms (palps) were red-brown. Although all were in the Clirysaora 

 condition and had only 3 tentacles and 4 lappets in each octant, some appeared to be fully 

 mature or with gonads nearly ripe. The exumbrella surface and the palps were covered 

 with dull milky-yellow clusters of nematocysts. There were 8 marginal sense-organs as in 

 Dact\lo>jietra, but only 24 tentacles and 32 marginal lappets. None of the medusae were, 

 however, as large as is commonly seen in full-grown Dactylometra quinquecirrha, the largest 

 Chrysaora-hke medusa seen in Norfolk harbor being only 105 mm. in diameter. It should 

 be borne in mind that D. /jiiinquecirrha does not usually attain 48 marginal lappets and 40 

 tentacles until the medusa is 120 mm. in diameter, and it seems therefore that the so-called 

 Chrysaora of the Chesapeake is only a stunted Dactylometra which becomes mature in the 

 Chrysaora stage, and its pale coloration may be a local peculiarity due to unfavorable 

 conditions of confinement in brackish water. In the purer ocean water at the mouth of 

 Chesapeake Bay the medusae develop into the Dactylometra condition with 40 tentacles. 

 These conditions are also found in Narragansett Bay, Rhode Island, where in relatively pure 

 clean water the medusae have 40 tentacles, but in brackish estuaries they often become 

 mature with only 24 tentacles and are pale in color. 



FIG. 373. Dactylometra ajricana, after Vanhbffen, in Valdlvia Expedition. 



Dactylometra africana Vanhb'ffen. 



Dactylometra afrifana, VANHOFFEN, 1902, Wissen. Ergeb. deutsch. Tiefsee Expedition, Dampfer Valdivia, Bd. 3, Lfg. I, p. 40, 

 taf. 4, fig. 20. 



Disk 100 to 130 mm. wide. 6 well-developed marginal lappets and 5 long tentacles in 

 each octant. Lappets and tentacles red. Red radial streaks over exumbrella. (Esophagus, 

 palps, and gonads not highly colored. Colors of large specimens duller than those of small 

 medusas and not unlike the coloration of D. quinquecirrha. Distinguished by its red lappets. 

 Coast of German Southwest Africa. Common in the Great Fish Bay on October 10, 1898. 



Dactylometra ferruginaster Kishinouye. 



Dactylometra ferruginaster, KISHINOUYE, 1892, Zoological Magazine, Tokyo, vol. 4, p. 264, taf. 3. 



Dact\jometra pacifica var. ferruginasttr, MAAS, 1909, Abhandl. Akad. Wissen. Munchen, Suppl. Bd. I, Abhandl. 8, p. 44, taf. 2, 

 fig. 14. 



Bell flatly rounded, 3 to 4 times as wide as high, 100 mm. in diameter. 48 oval, marginal 

 lappets. The 8 primary tentacles longer than the others. The lappets next to the ocular 



