372 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. rjuno 19, 



he examined my collection, and verified the greater number of the 

 species which I had obtained during the last ten or twelve years. The 

 Brachiopoda had previously been examined by Mr. Davidson, who 

 figured several of the most remarkable in his Devonian Monograph. 

 I am further indebted to Mr. Etheridge for his kindness in adding to 

 my list the name of the author by whom each species was originally 

 named. 



2. Subdivision of the Noeth Devon Rocks. 



The series of slates and sandstones to which the present paper 

 will be confined is bounded on the north by the Bristol Channel, 

 and on the south by the great trough of Carboniferous grits, which 

 extends far into the middle of the county. The beds of slate and 

 shale which divide this true Carboniferous deposit from the Devonian 

 can scarcely yet be assigned with certainty to either of these forma- 

 tions ; and to avoid, therefore, the confusion which would arise by 

 classing these intermediate beds with either of the other well-defined 

 rocks, I shall still continue to use the term *^ North Devonian," which 

 I have before applied* to the entire series which lies nol^th of the 

 town of Barnstaple. 



Prom the Foreland on the north to Barnstaple on the south the 

 rocks have an almost uniform dip to the south, usually at a high 

 angle; and in such a wide series, presenting to all appearance an un- 

 broken succession, it is especially important to be able to show that 

 throughout the whole of this area there exists a marked difference 

 in the distribution of species, both as regards variety of genera and 

 abundance of individuals, thus justifying the conclusions which 

 had been formed .by previous observers, who had based their sub- 

 divisions of the North Devon system rather on the lithological 

 structure of the beds than on the evidence of the fossils contained 

 in them. 



The accompanying sketch map is intended to show the relative 

 position and extent of the North Devon beds. 



In ascending order there are : — 



1st. The unfossiliferous grits of the Foreland, which rise out of the 

 Bristol Channel, and to all appearance form the lowest member of the 

 series. 



2nd. Lynton beds, consisting of hard grits, shales, and sandstones, 

 intersected with occasional bands of calcareous and ferruginous 

 matter. These beds contain a few species of fossils, principally 

 Orthis arcuataf, Spirifers, and Crinoids, aU of which, from the 

 extreme hardness of the stone, can only be obtained in the shape of 

 impressions and imperfect casts. At Woodabay and Lynton the 

 best sections may be seen. 



3rd. Martinhoe bed. Unfossiliferous grits and shales. 



4th. Ilfracombe group. A series of silvery slates and shales, 

 containing several thick bands of limestone, which, on being either 

 polished or exposed to the action of the air, show the outhnes of 



* Geology of North Devon, p. 7. 



t This species probably includes also the Orthis longisulcata of Phillips. 



