118 



MANUAL OF THE MOLLTJSCA. 



known to show that at least ten great changes had taken place 

 before the Secondary epoch. 



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

 the Formations or Periods ; the second contains those by which 

 the principal strata are known. 



I. QEOLOaiOAL TABLE. 



roitMATIONS OB 



Periods. 



Names of STeata. 



S3 

 O 



< 

 3h 



< 

 O 



/ 1. Tremadocian 



I- \ 



I 2. Snowdonian... 



jj j 3v Wenlock 



( 4. Ludlow 



( 5. Hercynian ... 



IIL ^ 6. Eifelian 



( 7. Clymenian ... 



■r-r;- f 8. Bernician 



• I 9. Demetian 



V, 10. Permian 



yj j 11. Conchylian ... 



( 12. Saliferous 



/l3. Liassic 



I 14 .Toarcian 



VIL -< 15. Bajocian 



1 16. Bathonian ... 



17. Oxfordian 



VIIL -I 18. CoraUian 



19. Kimmeridgian 



20. PortlancUan... 



(21, Wealden 



IX ^ 



122. Neocomian .. 



'23. Albian 



24. Cenomanian 

 X. -^25. Hippuritic ... 



26. Senonian 



(27. Londinian 



^^' ]28. Nummulitic... 



Xn. 29. Falunian 



XIIL 30. Icenian 



( Longinyn d slate . ( Bangor, Wicklow. ) 



^ Lingula flags = Primordial group. (Barrande.) 



( Tremadoc slate. Potsdam sandstone. 



f Llandeilo flags 1 Bala or Coniston 



\ Caradoc sandstone J group. 



J May-hill sandstone = Clinton gi'oup. 



( WooUiope and Dudley limestones. 

 L. Ludlow, Aymestry lime., U. Ludlow. 

 Spirifer sandstone ; Khine. ) Devonian and 

 PljTnouth limestone. > Old Eed 



Petherwin limestone. ) Sandstone. 



Carboniferous limestone (shale and coal. ) 

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

 Magnesian lime = Zechstein. (Perm.) 



f New Eed sandstone = Bunter. 



\ (Muschel-kalk = Ceratite limestone). 

 Red marls = Keuper. Lias bone-bed. 

 L. Liaa = Sinemurien and Liasien, 

 Marlstone, Alum-shale. (Thouars.) 

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



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



I Bradford cl. Forest m. Com brash.) 



r Kclloway rock = Callovien, D'Orb. 



\ Oxford clay. (White Jura.) 

 Coral-rag and Calcareous grit. 

 Kimmeridge clay. (Dorsetshire.) 

 Portland stone and Purbeck beds. 

 Hastings sand and Weald clay. 



f Speeton clay ? (Neuchatel). 



( Lower Green-sand, and Apfien, D'Orb. 

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

 Upper Green-sand. (Mans, Cenomanum.) 

 Chalk-marl and L. Chalk = Turonien. 



( Chalk with fUnts = BacuUte limestone. 



( Maestricht chalk = Dcmien, D'Orb. 



Thanet sands. Plastic clay, London clay, 

 j Bracklesham ; Barton ; 1. Wight ; = Parisie)i. 

 \ 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 make them more nearly equal in value.* 



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

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



