s^ 



and the Palaeozoic System of England. 363 



Lower Division continued, 



a. May Hill sandstone and Pentamerus,or 

 Norbury limestone. 



b. Woolhope (or Lower Wenlock) lime- 

 stone. 



c. Wenlock shale. 

 ^ d. Upper (or great) Wenlock limestone. 



r a. Lower Ludlow rock. 

 5. Ludlo. group I*; te'/lJirlrv" 



4. Wenlock group .... 



Upper Ludlow rock. 

 d. Tilestone. 



The introduction of the May Hill sandstone as a part of the 

 Wenlock group is the only change I have made in this portion 

 of the ' Tabular View/ which is prefixed to the ' Second Fasciculus 

 of the Cambridge Palaeozoic Fossils.^ It gives a true physical 

 and palseontological base to the Silurian series ; and assuredly 

 there is not (under this arrangement) any such thing in nature 

 as a " Middle Silurian Group/^ which inseparably links together 

 the Cambrian and Silurian series, and makes them into one 

 system. 



II. Middle Palaeozoic Division. 



{Devonian Series or Old Red Sandstone.) 

 In Herefordshire and South Wales. 



1. Comstone group Cephalaspis, &c. 



2. Red sandstone and conglomerate HoloptycMus, &c. 



In Devonshire and Cornwall. 

 1 . Liskeard and Ashburton group. 



{a. Great Devon limestone. 

 b. Calcareous slates. 

 c. Coarse red sandstone and flagstone, 

 r Coarse roofing slates, ending in North 



3. Dartmouth slate group -j Devon, with beds of red, green, and 



L variegated sandstone. 



{a. Marwood sandstone. 

 b. Petherwin slate and Clymenia lime- 

 stone. 



In Devon and Cornwall the above series has no base ; and 

 we are without any good evidence as to the beds below the 

 lowest Devonian group. Hence there is much uncertainty as 

 to the exact coordination of the series of Herefordshire with that 

 of Cornwall ; for the Herefordshire comstone has characteristic 

 fishes without characteristic shells and corals ; while the Devon- 

 shire and Cornish series has characteristic shells and corals, 

 but is without fishes. 



In a former scheme* the Liskeard and Plymouth groups 

 were united ; but they may, I think, be conveniently separated, 



* Advertisement to the Second Fasciculus of the Cambridge Palaeozoic 

 Fossils. 



2B2 



