48 CLASS I.— ORDER I. 



oval, oblong, and projecting ; opening marginated, and 

 nearly pentagonal. 

 On the Fucus natans. 



TOOTHED. 



20. Flustra dentata. Incrustation; but fre- 

 quently foliated; cells nearly oval, shining, and 

 toothed at the border. 



European seas. 



SQUARE. 



21. Flustra quadrat a. Incrustation ; cells form- 

 ing a long regular quadrangle with even borders. 



On the Fucus pyriferus. 



Variety on the fossils in the vicinity of Paris. 



triacanthous. 



22. Flustra triacantha. Incrustation; cells oval 

 or round, with two side thorns on the upper part, and 

 one on the lower. 



On the Thalassiophytes of Australasia. 



many-toothed. 



23. Flustra multidentata. Incrustation ; cells 

 large and nearly round ; opening garnished with many 

 long unequal teeth. 



On the fucus of Australasia. 



lanigerous. 



24. Flustra eriophora. Incrustation; cells very 

 small, alternate, round at the summit, covered with 

 unequal and numerous hairs. — Plate 1. fig. 5. 



On the fucus of Australasia. 



