216 
CLASS III. — ORDER II. 
they are likely to be the iirst to attract the attention 
of naturalists travelling with a view to study the ana- 
tomy and physiology of the animal inhabiting the 
Coralline and flexible Polypidoms. 
HETEROPOROUS. 
1. Flex aura heteropora. But slightly branching, 
and dichotomous ; cells distant, and dispersed ; open- 
ing long, pointed at each extremity, but irregular, 
and bending in all directions ; colour, a red fawn ; 
height from three to five decimetres ; diameter at least 
a centimetre and half. 
Porto Pico and Antilles. 
LARGE-CELLED. 
2. Plexaura macrocyttara. Stem branching; 
branches almost dichotomous, covered with large 
unequal cells, and almost all touching one another ; 
fawn colour ; height from three to six decimetres. 
Habitation unknown. 
THICK. 
3. Plexaura crassa. Cylindrical, and dichoto- 
mous ; branches thick, remote, and straight ; cells 
dispersed ; rind violet colour. 
American seas. 
FRIABLE. 
4. Plexaura friabilis. Stem and branches dicho- 
tomous ; cells round, of unequal size, and rather re- 
mote from each other ; colour, a tarnished fawn ; 
height from three to five decimetres# 
Indian Ocean. 
