52 
CLASS I.— ORDER I. 
communicating together underneath, with one or more 
bristly appendages on the outside, having their open- 
ing generally on the same surface. They have no 
distinct stem. 
PHERXJSA. 
Fron descent Polypidom with many clefts. Cells 
oblong, projecting, and placed only on one surface; 
openings irregular. 
The Pherusas differ so materially from the Flus- 
tras, that an eye the least exercised cannot pos- 
sibly confound them with the numerous species of 
that genus, nor with the Celleporas; though, like 
the latter, they have distinct projecting cells, but not 
isolated like them, as the Pherusas communicate at 
their base. They are equally removed from the Plus- 
tras by the situation of their cells ; in this latter, when 
the Polypidom is frondescent or foliated, the cells are 
found on both surfaces ; in the Pherusa they are al- 
ways placed on the upper surface, the under part 
being perfectly devoid of them, but shining and 
marked with nerves, corresponding to the partitions 
at the base of the cells. 
The Polypidoms of this genus have tubular cells, 
projecting in the upper part, large and compressed 
below: the opening is large, and usually irregular, 
with the border turned in, perhaps resulting from 
desiccation. Those at the extremity of the branches 
are nearly straight ; the others become less so in pro- 
portion as they approach the base. 
