1854,] HAMILTON MAYENCE BASIN. 271 



1 . Cerithium-limestone ; generally compact and close-grained, 

 containing C. margaritaceum and Dreissena Brardii, with here and 

 there a cast of Helix ; the lower portion of this bed is almost un- 

 fossiliferous, and seems to rest upon more marly heds. Its thickness 

 is at least 50 feet. 



2. Compact limestone, full of a small species of Cerithium, 

 Neritina, and Dreissena; about 10 feet. 



3. Limestone-beds, containing a large Cerithium, Dreissena, and 

 Cyrena Favjasii ; about 4 feet thick. 



4. Alternating beds of sand and marl. The lowest sandy beds 

 are full of Littorinella ; I am, therefore, disposed to look upon these 

 beds as marking here the junction between the Cerithium and Litto- 

 rinella limestones. They have a thickness of about 30 feet. 



5. A bed of broken fragments. 



6. Alternating beds, containing Littorinella and Cyrena. The 

 Littorinella generally occurs in the harder beds. Some of the 

 Cyrena-beds are completely made up of casts of that shell. 



7- Sand. 



8. Littorinella-limestone, alternating with marls and sands. Thick- 

 ness uncertain. This is the same formation as that which is seen at 

 the Kastrich in Mayence. 



9. Diluvial gravel ; 2 feet. 



10. Loess; 3 feet. 



11. Soil. 



3. Oppenheim. The lowest bed in the quarries at this place con- 

 sists, like those of Weissenau, of compact limestone, containing very 

 few fossils, and those chiefly Cerithium. A few bones are said to 

 have been found here. It belongs evidently to the Cerithium-lime- 

 stone. Above it are beds with Mytilus Faujasii, and a bivalve 

 {Cyrena subaratal or Venus incrassata) . Near the top of the sec- 

 tion is a loose marly limestone, containing angular fragments of 

 limestone, immediately overlying the oolitic-looking rock which in 

 some places appears to form the upper portion of the Cerithium-kalk. 



V. Upper Blue Clay. (No. 6 of the German list, page 260.) 



The Littorinella-limestone is immediately overlaid by the Upper 

 blue Clay or Upper Brown-coal Clay. I had no opportunity of 

 observing it, except in the small section near Hochstadt (fig. 9, 

 page 267), where it contains a small Cerithium and Cijrena Faujasii. 

 It is, however, in some respects a very important formation, as con- 

 taining the brown-coal beds of the Wetterau, the Westerwald, and 

 the Middle Rhine, which are extensively worked and are remarkable 

 for the interesting flora they contain. Some account of this flora 

 will be found in the above-mentioned works of Walckner, Sandberger, 

 and Voltz. It is, however, possible that the marly beds which 

 overlie the Littorinella-limestone in the Miihl-thal, near Wiesbaden, 

 are the representatives of this formation. In the second quarry from 

 Wiesbaden, down the Miihl-thal, is a section of 10 or 12 feet of 

 yellow, green, and dark-coloured marls, without fossils, overlying the 



