22 



PALEONTOLOGY 



side, and they are less crowded: it characterises Barrande's 

 division E of the Lower Silurian beds of Bohemia* and 

 occurs in the Llandeilo rocks in Britain. The Graptolites 

 abound in argillaceous strata, especially in the mud-stones of 

 Wales in Cumberland, and in the alum-slates of Sweden. 



Fig. 3. 

 Hydrozoa ; Anthozoa ; Bryozoa. 



i. Protovirgularia dichotoma, M'C. ; Silurian, Dumfries. 



2. Oldhamia antiqua, Forbes; Cambrian, Wicklow. 



3. Graptolites priodon, Brim. ; Silurian, Britain. 



4. Didymograpsus Murchisoni, Beck ; L. Silurian, Wales. 



5. Diplograpsus folium, His. ; L. Silurian, Britain. 



6. Bastrites peregrinus, Barr ; Silurian, Boliemia. 



7. Coenites juniperinus, Eichw. ; U. Silurian, Dudley. 



8. Ptilodictya lanceolata, Lonsd. ; U. Silurian, Tortworth. 



9. Archimedipora Archimedea, Lesuer. ; Carboniferous, Kentucky. 



10. Ptilopora pluma, M'C; Carboniferous, Ireland. 



11. Fenestrella membranacea, Ph.; Carboniferous, Britain. 



These beds remind one of the mud bottoms in which the 

 Virgularia and other long and slender graptolitic forms of 

 " Pennatulidoe" flourish in forest-like crowds. The primeval 

 Graptolite may have presented a more generalized polype 

 structure than is now met with in the specially differentiated 

 Sertularians and sea-pens. 



* " Graptolites de Boheme," 8vo, 1850. 



