118 



MANUAL OF THE MOLLrSCA. 



known to sliow tliat at least ten great cliauges had takon place 

 before tlie Secondary epoch. 



In the following Table, the first column gives the names of 

 the Formations or Periods ; the second contains those by "which 



the princijDal strata are known. 



I. GEOLOGICAL TABLE. 



foeiiations oe 

 Peeiods. 



31 





/' 1. Tremadocian 



I 2. Snowdoaian... 



jj j 3. Wenlock 



( 4. Ludlow 



( 5. Hercynian ... 



III. ' 6. Eifelian 



' 7. CljTneniau ... 



jy f 8. Bernician 



■ \ 9. Dcmetiau 



V. 10. Permian 



yj JU. Concliylian ... 



1 12. Saliferous 



/l3. Liassic 



I 14 .Toarcian 



VII. -| 15. Bajocian 



I 16. Bathonian ... 



17. Oxfordian 



VIIL i 18. Corallian 



19. Kimmeridgian 



20. Portlandian... 



(21. Wealden 



IX J 



\22. Neocomian .. 



'23. Albian 



21. Cenomanian 

 X. -i 25. Hippm-itic ... 



26. Senonian 



(27. Londinian 



XI ^ 



' |2S. Nummulitic... 



XII. 29. Faluniau 



XIII. 30. Icenian 



Names of Strata. 



i Longmynd slate. (Bangor, "NVicklow. ) 



J Lingula flags = Primordial gi-oup. (Baixande.) 



( Tremadoc slate. Potsdam sandstone. 



f Llandcilo flags \Bala or Coniston 



[ Caradoc sandstone J group. 



( May-liill sandstone — Clinton gi-oup. 



\ Woolliope and Dudley limestones. 

 L. Ludlow, Ajnnestr}' lime., U. Ludlow. 

 Spirifer sandstone ; Rhine.) Devonian and 

 PljTHOutli limestone. > Old Eed 



Petherwin limestone. ) Sandstone. 



Carboniferous limestone (shale and coal. ) 

 Coal-measures. (Millstone-grit, coal, &c.) 

 Magnesian Ume = Zechstein. (Perm.) 



f New Eed sandstone = Bunter. 



\ ( Muschel-kalk = Ceratite limestone). 

 Red marls = Keuper. Lias bone-bed. 

 L. Lias = Sinemurien and Liasien. 

 Marlstone, Alum-shale. (Thouars.) 

 Inf. Oolite, FuUer's-earth. (Bayeux.) 



f Great Oolite. (Stonesfield slate ; G. Uol. 



I Bradford cl. Forest m. Cornbrash.) 



f Kelloway rock = Callovien, D'Orb. 



\ Oxford clay. ("White Jura.) 

 Coral-rag and Calcai-eous gi-it. 

 Kimmeridge claj'. (Dorsetshire.) 

 Portland stone and Purbeck beds. 

 Hastings sand and "Weald clay. 



f Speeton clay ? (Neuchatel). 



\ Lower Green-sand, and Aptien, D'Orb. 

 Gault. (District of the Aube, or Albe.) 

 Upper Green-sand, (Mans, Cenomanum.) 

 Chalk-marl and L. Chalk = Turonien. 



S Chalk with flints = Baculite limestone. 



\ Maestricht chalk = Danien, D'Orb. 



Thanet sands, Plastic clay, London clay, 

 j Bracklesham ; Barton ; I. "Wight ; = Parisien. 

 \ Hempstead ; Fontainblean ; = Tongrien. 



Faluns of Touraine ; Bordeaux, Vienna. 



Crag of E. Co. = Sub-apennin, D'Orb. 



It must be observed that the number and magnitude of the 

 " Formations " was determined by accident in the first instance, 

 and afterwards modified to suit the requirements of theory, and 

 to mako them more nearly equal in value.* 



* The names of formations are in great measm-e provisional, and open to criticism. 

 Some of them were given by Brongniart and 0. D'Halloy ; others have been more 



