6 



PALEONTOLOGY 



M. d'( Irbigny enumerates 30 genera and 1 27 species of 

 fossil sponges; and this is probably only a small proportion 

 of the actual number in museums, as the difficulty of deter- 

 mining the limits of the species is very great, and many 

 remain undescribed. 



Palccospongia and Acanthospongia occur in the lower Silu- 

 rian ; and Stromatopora, with its concentrically laminated 

 masses, attains a large size in the "Wenlock limestone. Ste- 

 ganodictyum, Spavsispongia, and species of Scyphia, are found 



Amoriiliozoa ; lihizojwda. 



i. Siphonia pyriformis, Goldf. ; Greensand, Blackdown. 

 %. Guettardia Thiolati, D'Arcb.; U. Chalk, Biarritz. 

 3. Ventriculites radiatus, Mant. ; V. Chalk, Sussex. 

 4 Manon osculiferum, Phil.; U. Chalk. Yorkshire, 



5. Fusulina cylindrica, Fisch. ; Carhoniferous. Russia 



6. Flabellina rugosa, D'Orb.; Chalk, Europe. 



7. Lituola nautiloidea, Lam. ; Chalk. Europe. 



8. Nummulites nummularia, Brug. ; /■'occur, Old World. 



9. Orliitoides media, D'Areh. ; U. Chalk, France. 

 10. Ovulites margaritula, Lam.; Chalk, Europe. 



in the Devonian; and Bothroconds, Mamillopora, and Tragos, 

 in the Permian or magnesian limestone. Several genera are 

 common to the trias and oolites, and several more are peculiar 



