G. FLUSTRA. 45 



PEAR-SHAPED. 



3. Flustra pyriformis, Foliaceous and dichoto- 

 mous ; summits truncated ; cells formed like a pyramid, 

 very sharp at the bottom ; height about one decime- 

 tre ; width in the middle of the branches from two to 

 four millimetres. — Plate 1. fig. 4. 



Australasia. 



ceranoidous. 



4. Flustra cer amides. Flower-like and dichoto- 

 mous ; summits bifid ; extremities obtuse ; cells long ; 

 mouth almost linear, with the border rolled over; 

 height from five to eight centimetres ; width in the 

 middle of the branch two or three millimetres. 



Australasian sea. 



BOMBYCINOUS. 



5. Flustra hombycina. Plant-formed, with ob- 

 tuse divisions, dichotomous or trichotomous ; cells 

 rounded ; foot root-formed. 



On the coast of Calvados, a reef of rocks bordering 

 on Normandy ; and also said to be found in the Indian 

 and American seas. 



flaxen. 



6. Flustra carbasea. Foliaceous, dichotomous, 

 and obtuse at the summit ; cells long and formed py- 

 ramidically. 



On the coasts of Scotland and Calvados. 



chartaceous. 



-7. Flustra chartacea. Foliaceous, digitated, and 

 truncated at the summit ; cells four-sided. 

 Coasts of England and France. 



