642 PKOCEEDINGS OF THE GEOLOGICAL SOCIETY. 



Devonian Rocks of IN'orth Devon, to which are added the species that 

 occur in the Quantock Hills and other localities in West Somerset, 

 chiefly from the Limestones east and south of Croydon Hill. It may 

 be largely added to by diligent search along the east side of the Quan- 

 tocks at Adscombe, Stowey, &c. &c. This table will form the basis 

 of my comparisons both with species that may range lower or higher 

 in this area, and also with the European Devonian fossils as collated 

 with our British types. 



This Middle division or group of the Devonian rocks, both in ITorth 

 and South Devon, has received most attention, arising partly from cir- 

 cumstances pecuhar to its geographical position on the one hand, 

 and to the economical value of its limestones on the other ; and this 

 applies to Europe as well as Britain. It is the source of the lime used 

 in the interior of IS'orth Devon ; in quarrying, therefore, the amount 

 of limestone removed is considerable; and it is to this circumstance 

 alone that we owe our knowledge of the Coelenterate fauna of the 

 Middle Devonian of North and South Devon. In the south, at 

 Torquay, Plymouth, &c., the excess of workable limestone over that 

 of the north is so great that long ago extensive collections were made, 

 the species carefully examined, and then justly referred by Lonsdale 

 to an extensive formation existing between the Silurian and Carboni- 

 ferous systems * — in other words, occupying the stratigraphical place 

 of the Old Red Sandstones, whatever may be the exact relation of 

 this marine Devonian group to that great and almost non-fossili- 

 ferous formation. 



Having enumerated the entire fauna as known in N"orth Devon, it 

 will be important to compare the species that are known to occur 

 in beds of the same age in South Devon to aid us in generalizing upon 

 the value of the term Middle Devonian, as now used, applied to, and 

 correlated with, the European groups. 



4. Species common to the Middle Devonian HocTcs of North and South 

 Devon. — It will perhaps surprise many to find that there are 235 

 marine species known in the Middle (or Torquay, I^ewton, and Ply- 

 mouth) group in South Devon, which are distributed through 11 classes 

 of the animal kingdom. I briefly enumerate the 11, also the genera 

 and species in each (Table Y.) 



* Proceedings Greol. Soc. 1840, vol. iii. ; Trans. Geol. Soc. vol. v. p. 721, 

 &c. &c. 



