46 
CLASS I.— ORDER I. 
STONY. 
S. Flustra ^raz. Foliaceous, fan-shaped, and 
proliferous ; summits rounded ; cells alternate, co- 
vered with small papillae, placed on two opposite 
lines ; height from three to four centimetres. 
On the Thalassiophytes of Australasia. 
TREE-FORMED. 
9. Flustra frondiculosa. Arborescent; divisions 
obtuse, trichotomous, and crowded ; cells placed one 
above the other. 
Indian Ocean. 
BRTSTLY. 
10. Flustra hispida . Arborescent and spongy ; 
divisions branching ; stuck and surrounded with hairs. 
Mediterranean sea ; very scarce. 
VELVET. 
11. Flustra pilosa. Foliaceous or covering Thalas- 
siophytes ; the under border of the cells with a bristly 
tooth. 
European seas ; usually on the Thalassiophytes, 
which it sometimes wholly covers, but does not in- 
crustate. 
DOWNY. 
12. Flustra tomentosa. Incrustation, soft and 
velvety ; cells scarcely visible. 
In the European seas, attached to Thalassiophytes 
and Sertularias. 
LINEAR. 
13. Flustra lineata. Incrustation ; cells situated 
on transverse and oblique lines. 
