GEMICELLAEIA. 297 



loriculata. It is not easy to account for the abounding 

 of certain species on some coasts, and the entire absence of 

 these very species on other coasts at no great distance. 



Genus GEMICELLAEIA. 



1. GEMICELLARIA BURSAPJA, Blainvitte. (Plate XYI. 

 fig. 59.) 



Hab. On seaweeds and corallines. Devonshire, Mrs. 

 Griffiths; Mr. Peach, Isle of Wight; Mr. Wigham, coast 

 of Norfolk; Mr. J. B. Hall, Isle of Wight, 



Nothing can be better than the description of Ellis, who 

 also gives an excellent figure of it in plate xxii., under the 

 name of the shepherd's-purse coralline. " This most beau- 

 tiful pearl-coloured coralline adheres by small tubes to Fuci, 

 from whence it changes into flat cells ; each single cell like 

 the bracket of a shelf, broad at top and narrow at bottom : 

 these are placed back to back, in pairs, one above another 

 on an extremely slender tube, which seems to run through 

 the middle of the branches of the whole coralline. The cells 

 are open at top. Some of them have black spots in them ; 

 and from the top of many of them a figure seems to issue 

 out like a short tobacco-pipe, the small end of which seems 



