618 



MEDUSAE OF THE WORLD. 



niches. The sense-club is covered by a prominent scale, beneath which it stands in an almost 

 vertical position. There is a deep exumbrella sensory-pit above each sense-club. There 

 appear to be no distinct velar lappets, the bell-margins being only slightly wavy, excepting for 

 the deep, rhopalar clefts. In Bigelow's large medusa 41 radial-canals arise from the periphery 

 of the circular central stomach, but two of these anastomose so that only 40 extend to the ring- 

 canal centripetal to the zone of the rhopalia. The ring-canal gives rise to a trident-shaped 

 diverticulum in the radius of each sense-club and to one or two simple, blindly-ending divertic-. 

 ula in the inter-rhopalar spaces. The canal-system, like the rhopalia, bears a striking resem- 

 blance to Phacellophora. The mouth parts appear also to be similar to those of Phacellophora 

 but are not well preserved in any specimen yet captured. The gonads form a nearly continuous 

 ring around the periphery of the subumbrella floor of the stomach. This ring is not truly con- 



FIG. 396. Poralia rufescens, after H. B. Bigelow, in Mem. Mus. Comp. 

 Zool. at Harvard College. 



tinuous, however, but is interrupted by 1 8 or 19 thickened, vertical ridges in the stomach-wall. 

 The gonads themselves thus consist of 18 or 19 outpocketmgs of the stomach-wall project- 

 ing outward. The numerous, simple, gastric cirri are arranged in a single line arising from the 

 stomach-wall on the inner side of the genital organs. The subumbrella is reddish-brown, the 

 gonads being paler. The tentacles were lost in all of the specimens so that we know nothing 

 of them. 



Vanhoffen's specimen came from a depth of about 350 fathoms between Queen Emma 

 Harbor and Siberut Island, Indian Ocean, and the two described by Bigelow were found by 

 the Albatross in the eastern part of the tropical Pacific. 



The radial-canals in this medusa appear toincrease in number with growth, for VanhofFen's 

 specimen which was only about 60 mm. wide had 21 canals, while Bigelow's 250 mm. wide 

 specimen had 41. VanhofFen's medusa had / or 8 (?) gonads, and both he and Bigelow believe 

 that the young medusa is probably octoradial. 



Subfamily AURELINJE L. Agassiz, 1862. 



The numerous tentacles and lappets arise from the sides of the exumbrella above the 

 margin. Gonads are invaginated sacs with external subgenital cavities. 4 simple or bifurcated 

 mouth-arms. 



