118 MANUAL OF THE MOLELUSCA. 
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. GEOLOGICAL TABLE. 
FORMATIONS OR NAMES OF STRATA 
PERIODS. 
{ Longmyad slate. (Bangor, Wicklow.) 
1. Tremadocian Lingula flags = Primordial group. (Barrande.) 
( 
7 § Tremadoce slate. Potsdam sandstone. 
ite Llandeilo flags Bala or Coniston 
a ( 2 SOD USUI. acces sandstone group. 
< § 3 Wenlock May-hill sandstone = Clinton group. 
S) Ase Roth enue BA Woolhope and Dudley limestones. 
34 ( 4. Ludlow ......... L. Ludlow, Aymestry lime., U. Ludlow. 
3 f 5. Hercynian ... Spirifer sandstone; Rhine.) Devonian and 
2 lil 6. Eifelian......... Plymouth limestone. Old Red 
q Leif Clymenian ... | Petherwin limestone. Sandstone. 
Ay | IV 8. Bernician...... Carboniferous limestone (shale and coal.) 
: 9. Demetian...... Coal-measures. (Millstone-grit, coal, &c.) 
\ Ve 0 Permian) fs... Magnesian lime = Zechstein. (Perm.) 
{ . New Red sandstone = Bunter. 
yr, Jil. Conchylian ... | (Nene — Ceratite limestone). 
| ( 12. Saliferous...... Red marls = Keuper. Lias bone-bed. 
a AGWASSIG em tecees L. Lias = Sinemurien and Liasien. 
| a -Toarcian ...... Marlstone, Alum-shale. (Thouars.) 
| VII. | 15. Bajocian ...... Inf. Oolite, Fuller’s-earth. (Bayeux.} 2, 
; |S Great Oolite. (Stonesfield slate ; G. Vol. 
\2 16. Bathonian | Bradtfordcl. Forest m. Cornbrash. ) 
<4 Kelloway rock = Callovien, D’Orb. 
oe a Oxfordian ..... Oxford clay. (White Jura.) 
fi, VILE Corallian ...... Coral-rag and Calcareous grit. 
A | 19. eu eereeien Kimmeridge clay. (Dorsetshire.) 
Z \ 20. Portlandian.. Portland stone and Purbeck beds. 
© 21. Wealden ...... Hastings sand and Weald clay. 
3 IX. > . Speeton clay? (Neuchatel). 
ie 22. Neocomian | Lower Green-sand, and Aptien, D’Orb. 
2A INNES Assocs Gault. (District of the Aube, or Albe.) 
24. Cenomanian Upper Green-sand. (Mans, Cenomanum.) 
X. < 25. Hippuritic ... | Chalk-marl and L. Chalk = Turonien. 
1 : Chalk with flints = Baculite limestone. 
\ 26. Senonian ...... eee chalk = Danien, D’Orb. 
A 27. Londinian...... Thanet sands, Plastic clay, London clay. 
a KA = yi Bracklesham ; Barton; I. Wight; = Parisien. 
a 28. Nummulitic... Ae aE Fontainblean ; zg Tongrien. 
ss XII. 29. Falunian ...... Faluns of Touraine; Bordeaux, Vienna. 
a} Ia OO AC enIAN 725 /e..00 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 yalue.* 
* The names of formations are in great measure provisional, and open to criticism, 
Some of them were given by Brongniart and O. D’Halloy; others have been more 
