GEMICELLARIA. 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 GEMICELLARIA. 
1. GemiceLtaria Bursaria, Blainville. (Plate XVI. 
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 
