//. S. Williams — Devonian System of Devonx/dre. , 33 



In North Devonshire the difficulty is not so great, but even 

 there the fossils are rare, and the contorted and slaty structure 

 of the beds, even without the occasional faults, lias caused 

 grave dispute as to the true relation of the beds. As classified 

 by Mr. Robert Etheridge, the North Devonshire section is 

 divided into Lower, Middle and Upper Devonian, as follows : 



Loiter. — The Foreland grits and the Lynton and Woodsbay 

 slates, with fossils in the Lynton slates and in limestone beds 

 intercalated in the higher part of the series. 



Middle. — Shales and slates with occasional thin beds of impure 

 limestone, from the Hangman and Trentishoe grits inclusive 

 of all the coast rocks of the north shore as far as to Morthoe. 

 The Lower beds, of Combe Martin and Haggington in their 

 calcareous layers holding the /Stringocephalus, or Middle 

 Devonian fauna, and the beds about Ilfracombe hold a some- 

 what higher fauna. 



Upper. — From the Pickwell Doinn Sandstones all the slates, 

 shales and grits with occasional calcareous streaks across to 

 the south line of North Devonshire at Barnstaple Bay (called 

 Marwood, Baggy, Croyde, Pilton, Barnstaple, etc., beds). 



It is with this section more particularly that the classification 

 of the New York system was compared in the first surveys. 

 And when we notice that the fauna we now consider as Lower 

 Devonian (i. e., that of the Corniferous limestones), is little 

 represented there and that the Hamilton fauna is largely made 

 up of species quite distinct from those of North or South Devon- 

 shire, it is not surprising that T. A. Conrad in the preliminary 

 reports of the State survey drew the line between the Silurian 

 and Devonian of the New York system at the top of the Ham- 

 ilton formation. Before becoming acquainted with them I 

 expected the original Devonshire sections and fossils to throw 

 some light upon the problem of proper classifications of the 

 Devonian system, but I came away convinced that for internal 

 evidence as to the order of sequence or even the precise com- 

 position of the faunas the Devonshire sections are extremely 

 unsatisfactory. It is probable that the fossils of the Plymouth 

 and Xew ton Bushel limestone formed the basis for the notion 

 of a Middle Devonian. These limestones furnished the fossils 

 which were recognized by Lonsdale, in 1839, as constituting a 

 fauna intermediate between the Silurian and Carboniferous, a 

 determination which resulted in the establishment of a new 

 system, the Devonian. It is, however, quite uncertain what 

 fauna followed or what preceded this limestone in South 

 Devonshire. The rocks about Pilton and Barnstaple, Mar- 

 wood and Sloly in North Devonshire furnished the originals 

 of the Upper Devonian fauna. The Ilfracombe fauna was 



Am. Jour. Sci.— Third Serieis, Vol. XXXIX, No. 229.— Jan., 1890. 

 3 



