692 PEOCEEIUNGS OF THE GEOLOGICAL SOCIETY. 



Davidsonia Verneuilii, and many other equally characteristic species 

 cease to be typical continental and British Middle-Devonian shells. 

 The limestones and gritty slates of Combe Martin occupy in North 

 Devon the same subordinate place in that series (being near the 

 base), as they do at Ecaussines, in Brabant, and they are unques- 

 tionably the equivalents in this country of the PafFrath and Miins- 

 ter-Eifel beds in the Ehenish provinces. 



I have endeavoured to show reasons why these beds reposing upon 

 the Hangman grits occupy a place far below the so-called Old Red 

 Sandstone of PickwellDown*. 



In South Devon we have no Upper Devonian rocks yet known, 

 and consequently no fossils referable to them. 



It has also been asked if '' the rocks of South Devon are not a 

 mere expansion of the [so-called] Carboniferous Slates of North 

 Devon, with a change in the fauna depending upon difference of 

 province." ISTo one who has examined the fossils or the rock-masses 

 of the two areas north and south of the granitic mass of the Dart- 

 moor can doubt their identity in time, either through organic remains, 

 or through similarity of physical structure, the chief and only dif- 

 ference being the greater development of the organic limestones 

 in the south over that of those in the northern area. There is no 

 change or difference in the fauna of the two regions ; and of the 

 238 species known in the Middle Devonian of South Devon 53 

 occur in the same series in North Devon, and that chiefly through 

 the corals and Brachiopoda ; and 21t of these 238 are known in 



* It is still an open question whether the Upper Devonian beds are repre- 

 sented in the Avon section or not. There is a series of grey shaly marls and 

 impure limestones beneath the Bone-bed which exists at the base of the Lower 

 Limestone Shales ; in one of these shaly beds are found Modiola Macadami, 

 Avicula Bamnoniensis, CucuUcea trapezium, C. Hardmgii, Filicifes dicJiotoma, 

 Knorria dichotoma, Naticopsis pUcistria, and other forms recognized in the Upper 

 Devonian beds of the Marwood series in North Devon. Underlying the bed 

 containing the above, there occurs 100 feet of alternating limestones, shales, and 

 marls, including about 30 feet of passage-beds into the Old Eed Sandstone, which 

 is recognizable by quartzose conglomerates. None of the above forms occur 

 higher, in the Carboniferous Limestone, not even in the intermediate and imme- 

 diately succeeding argillaceous Lower Limestone Shales ; but true Carboniferous 

 species are associated with them, such as Spirifera bisulcata, Streptorhynchus 

 crenistria, ShyncJionella pleurodon, Orthoceras gregarium, Lingulamytiloides. All 

 the above facts were carefully noted and described by W. W. Stoddart, Esq., F.G-.S., 

 in a communication read at the Bath Meeting of the British Association, 1865, 

 Trans, of Sections, p. 71. I have since examined and measured the entire section 

 underlying the red crystalline limestone band which forms so conspicuous a 

 feature below the Fish- or Bone-bed ; and whatever these impm'e limestones, 

 grits, and shales may be, they are a very distinct group from either the red con- 

 glomerates and marls below, or the overlying argillaceous limestones, which con- 

 stitute the well-defined so-called Lower Limestone Shales, which are 500 feet 

 thick : this passage-series may, and probably does, represent the greatly developed 

 Upper Devonian beds of Baggy and Marwood above the Upper Old Eed Sand- 

 stone of Pickwell Down ; before the chief mass of thick-bedded flaggy Old Eed 

 Sandstone and marls are reached, the ground is occupied by a highly siliceous 

 variegated marly series, measuring 1000 feet, which is indicated by the valley 

 east of the railway-tunnel. 



t 3 Polyzoa, 8 Brachiopoda, 3 Lamellibranchiata, 4 Gasteropoda, and 3 Cepha- 

 lopoda. 



