MUSEUM OF COMPARATIVE ZOOLOGY. 139 



cisions between the marginal lobules. Each pair of otocysts is separated by 

 three tentacles. From the alcoholic specimens I could not determine their 

 ultimate structure. They are mounted on a short style, and seem to resemble 

 closely the otocysts of Pelagia. The structure of the under floor of Polybostrica 

 is very peculiar. The oral appendages are joined together, forming a cylin- 

 drical body with a terminal mouth opening. This complicated labial ap- 

 pendage hangs from the lower floor at four points, where the walls are thicker 

 than in intermediate portions. The part of the cylinder between two supports 

 is inflated, hanging down in a bag shape. 



The ovaries were partially destroyed, but enough of them remained to show 

 that in their position they alternate with the attachments of the oral ap- 

 pendages, and that the ovarian tentacles are very large. 



The size of the jelly-fish in alcohol is more than eight inches in diameter. 

 Smaller examples were also taken, which were an inch or an inch and a half 

 across. 



Cambridge, March 1, 1881. 



