CONTRIBUTIONS TO THE BRITISH FAUNA. 243 



transparent and brittle, is about ari inch and a half 

 in length. 



This shell, like several of its congeners, is gre- 

 garious, and is usually found in clusters attached 

 to a white gelatinous spherical substance, which 

 adheres to various bodies. 



The most curious circumstance in the history 

 of this species, is the rapidity of its growth. The 

 gelatinous substance from which the peduncles 

 that support the Shells proceed, is found adhering 

 to various species of fuci, pieces of wood ; and 

 what is still more remarkable, I onte observed full 

 grown specimens adhering to the quill-feather of a 

 gull. The feather seemed very entire and fresh. 

 Flustra membranaced sometimes covers it all 

 over, and so completely incloses the mouth of the 

 shell, as to destroy the inhabitant. It is likewise 

 infested with Sertularia geniculata ^. 



This shell was first observed by Ellis previous to 

 the year 1776, and figured by him (Ellis, Zooph. 

 tab. 15. fig. 6,) from a specim.^ from St George's 



0^2 ^ 



* Pallas, when speaking of Loefling's observations on Sertii« 

 laria geniculata, says^ Vitam torpidissimam habere polypos 

 dicit, ut acu tacti vix sensibilitatis dent signa." Elenchus Zooph, 

 p. 119. This character of torpidity is by no means applicable 

 to the S. geniculata of Ellis. When I touched the animals of 

 this coralline with a needle, they speedily retired within the ca- 

 vity of their cups ; and when pulling away a small ascaris, which, 

 by its motions, disturbed my observations with the microscope^ 

 It was instantly seized and devoured by one of these animals. 



