216 CLASS III.— ORDER II. 



they are likely to be the first 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. Plexaura 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 Rico 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. 



