OBELIA PLICATA. 159 



Referred provisionally to this genus. 



6. O. PLICATA. 

 Plate XXX. fig. 1. 



SHOOTS clustered; MAIN STEMS composed of a large number 

 of very slender, flexuous tubules bound together, thick 

 below and tapering upwards, sending off a multitude of 

 branches ; BRANCHES, some compound, and some simple 

 and very delicate, of great length and much ramified, 

 annulated above the origin of the branchlets ; HYDRO- 

 THEC/E alternate, broadly campanulate, even-rimmed, and 

 borne on ringed pedicels. 



GONOTHEC^E unknown. 



Height between 3 and 4 inches. 



THE only other British Obelia which has a thick compound 

 stem, the O.gelatinosa, differs widely from O.plicata in its 

 habit of growth and in the character of its hydrothecae. 

 The latter species forms large clusters of shoots, which 

 are remarkable for their luxuriant ramification. The main 

 stem is a bundle of delicate tubes closely adherent to one 

 another, and gives off branches at short intervals; those 

 on the lower portion are thick and compound, those above 

 becoming gradually more slender, until towards the ex- 

 tremity of the shoot they are perfectly simple. The stem 

 itself, of course, diminishes proportionately as bundle 

 after bundle of the tubular strands that compose it is given 

 off, and tapers away towards the top. The branches are 

 very long, and clothe the stems densely to the summit ; 

 they are generally much ramified, so that the habit of the 

 species is eminently shrubby and luxuriant. 



The calycle very much resembles in form that of O. 

 dichotoma. 



Hab. Shetland (J.G.Jeffreys). 



