306 Mr. Weaver's F?Vw o/'Ehrenberg's Observations 



Atlas, and of Arabia from Sinai to Lebanon, thus opening a 

 large field to organic distribution. 



5. Many of the chalk-like formations bordering on the Me- 

 diterranean in Sicily, Barbary and Greece, really belong to 

 the period of the European chalk formation, as proved by 

 their organic contents, although commonly held to be differ- 

 ent from the chalk, and considered as tertiary *. 



6. The chalk beds of the South of Europe, around the ba- 

 sin of the Mediterranean, are distinguished from those of the 

 north and east of Europe by numerous well-preserved chalk 

 animalcules, and less numerous inorganic lamina; while in 

 the north and east of Europe these relations are reversed f. 



7. In the South of Europe the beds of marl which alternate 

 with the chalk consist of siliceous shells of Infusoria, and flints 

 are wanting; while in the North of Europe beds of flint al- 

 ternate with the chalk, and marls with Infusoria are wanting. 

 This exchange of character tends to explain the peculiar re- 

 lation of flint to chalk, indicating that the pulverulent sili- 

 ceous particles of Infusoria have been converted into compact 

 nodules of flint. 



8. It has been lately remai'ked that the chalk which con- 

 tains flints is deficient in numerous siliceous Infusoria, when 

 compared with the Bilin slaty Tripel or polishing slate (Po- 

 lirschiefer) containing semi- opal ; but this deficiency now dis- 

 appears, and a rich substitute takes its place, the Infusoria in 

 the North of Europe having been employed in the formation 

 of flints; while in the south, remaining unchanged, they are 

 preserved in the Infusoria marls. 



9. The chalk animalcules resemble most those of the sea- 

 sand and the Miliolites, which, up to the present day, have 

 been ranged among the Mollusks with the Cephalopods ; but 

 neither of these are either Cephalopods or Mollusks, nor even 

 Infusoria (as asserted by a late observer) ; but they are Bry- 

 ozoa, animals of Moss-corals, which are most nearly related 

 to Flustra and Eschara. 



10. The sea downs of some, and probably of most coasts, 

 are still in course of formation by living Bryozoa, which, 

 though very small, resembling grains of sand, are yet, for the 

 most part, larger than the chalk animalcules, and a large pro- 



* In Sicily, however, there occur many breccias of chalk, which have 

 suffered a subsequent change, and may be referred to the tertiary epoch. 



\ Thus in the white and yellow soft writing chalk of the North of Europe 

 the inorganic crystalloid portions sometimes equal or rather exceed in mass 

 the organic remains ; but in the South of Europe, in Sicily, these organisms 

 with their fragments are greatly predominant, consisting, as it appears, ex- 

 clusively of well-prererved Polythalamia. 



