50 CLASS I.— ORDER I. 



TESSELLATED. (FOSSIL.) 



31. Flustra fessellata. Incrustation, thick; parti- 

 tions rounded in the fore part; openings in front, small 

 and nearly round ; top of the cells flat and thick, of 

 an ivory white, and very shining. 



On the fossils of the chalk in the vicinity of Paris. 



CRETACEOUS. (FOSSIL.) 



32. Flustra cretacea. Thick incrustations, with 

 long oval cells. 



On fossil shells in the vicinity of Plaisancc, analo- 

 gousto the MurexTritonis of our seas. 



RETICULAR. (FOSSIL.) 



33. Flustra reticulata. Rather thick, forming 

 free expansions, celluliferous on both surfaces ; cells 

 oval and long, the partitions very projecting ; openings 

 middling in size, and rather transversal. 



In the sand near Valogne in France, with Bacu- 

 lites and Beleraites. 



bifurcated. (FOSSIL.) 



34. Flustra bifurcata. Foliaceous, dichotomous 

 expansions, bifurcated at the summits, and garnished 

 with hexagonal cells on both surfaces. 



At Grignon, and in a lime- stone at Cerithes. 



BOTTLE-SHAPED. (FOSSIL.) 



35. Flustra utricularis. Incrustation in very 

 spreading expansions ; cells oval and a little flat- 

 tened, larger at the back, with rather a small opening 

 placed in front. 



