SOME MEDUSA OF JAPANESE WATERS. 11 



of uüibrella, the shape and size of nematocysts as well as their 

 distribution on umbrella, the shape of marginal lobes, the length 

 of the oral tube and of oral arms, the coloration, etc. However, 

 these characters are subject to considerable variation according to 

 the age of individuals, and even among those in same stage of 

 growth and simultaneously collected in the same locality. 



Chrysaora convolata, u. sp, 



(PI. II, Figs. 11-14.) 



The umbrella is somewhat vaulted, its height being contained 

 about three times in the breadth. The umbrella-margin is divided 

 into thirty-two lobes, which have rounded margin. The ocular 

 lobes are broader than other marginal lobes, while the tentacular 

 lobes are slightly longer than the ocular lobes, which are subdivided 

 into two unequal lobes by a slight incision at the point of origin 

 of radial cathamma. The adradial incision between tentacular 

 lobes is deeper than the incision between tentacular and ocular 

 lobes. The coronal portion of umbrella hangs down nearly 

 vertically, and makes an angle with the remaining portion. The 

 gelatinous substance of umbrella is thick and tough. 



The exumbrella is smooth, and presents a brown, sixteen 

 rayed, star-shaped figure, the rays having straight boundaries. 

 The broad centre of the figure is colorless. The rays disappear 

 in the hanging coronal parts. There are many brown spots of 

 irregular size, shape and distribution between the rays. 



In the subumbrella are found sixteen, narrow, dark brown, 

 radiating rays on the lower side of the radial cathamma or the septa 

 between radial pouches. The oral pillars are remarkably well deve- 

 loped, leave a narrow slit between every two of them, and consist 



