ETHERIDGE DEYONIAN ROCKS AND FOSSILS. 655 



systems (Devonian and Carboniferous), which can hardly be regarded 

 in our calculations, much doubt existing as to their position ; regard- 

 ing them, however, as strictly passage-species and common to either 

 group, we have 49 species belonging to this horizon. Xone are 

 ■peculiar to the Lower Devonian of either Xorth or South Devon ; 

 whereas 35 species are not known out of the Middle, and four are 

 common to Lower and lliddle, viz. Alveolites suhorhicularis, Lam., 

 Favosites cervicornis, Blainv., Petraia celtica, Phill., and Pleuro- 

 dictyimi problenutticum, Goldf. * "When we compare this important 

 group of fossils with their equivalents in the Ehenish provinces, Bel- 

 gium, and France, we find that 22 out of the 51, or 43 per cent., 

 are identical species with those found in the three areas on the Conti- 

 nent, 17 are Ehenish, 14 are Belgian, 11 are common to both areas, 

 and 11 occur in the Boulonnais. 



The accompanying Table (TIL) shows the distribution of those spe- 

 cies only that are known to be common to Britain and Europe in 

 either the Lower, Middle, or Upper division : 35 are absolutely con- 

 fined to the Middle Devonian series of South Devon ; and 22 of these 

 occur in Europe ; see Table II., p. 616, and Table Y., p. 643 ; so 

 that the relation of an area to the species that occupy it, the entity 

 of the Middle Devonian Corals amongst themselves, with other 

 equally definite physical conditions, palaeontological affinities, and 

 results, in aU the areas, give a marked and peculiar character to the 

 Middle Devonian group : 3 species only of the 22 (Table YII.) occur 

 in the Upper Devonian beds of Xorth Devon, as we should expect fi'om 

 the nature of the sea-bottom ; and two of these belong to the Turbino- 

 liae, or simple foims, whose habits are different from those of the com- 

 pound species; they are Amplexus tortuosus,'2\ni., and Petraia Celtica, 

 Phill., the remaining species being the dubious Fistuhpora (Manon) 

 crihrosa, Goldf. ; and no single species of the hnown 51 passes up to the 

 Carboniferous system. It cannot, then, be asserted that we have no true 

 Devonian Corals, or that there "are or were local coral-banks in the 

 Carboniferous sea," when no single form is known common to the two 

 horizons, either here or in any hnoivn area : such reasoning would not 

 and could not apply either to the great assemblage of Corals and 

 Crinoidea in the Upper SUurian, or to the Corals of the Carboniferous 

 Limestone, where the suiTounding relations are the same ; they, hke 

 the species in the limestones and slates of the Middle Devonian 

 series, were a group peculiar to themselves, and to the seas in 

 which they lived, and as definitely determine it. This class, like 

 the Brachiopoda, which wiU claim our next attention, occupies and 

 typifies one physically united area, dying out or changing when 

 the conditions favourable to their existence no longer continued ; and 

 the continuous or fringing barrier-like reef of slatj' coral and lime- 

 stones which extends //-om ivhat is now Ilfracombe and Combe Martin 

 to the Quantock Hills, in West Somerset, and farther east still, under 

 the Secondary rocks, ceased to exist as the area they then occupied 

 deepened, or became depressed, thus giving origin to the grey fine- 

 grained sedimentary non-fossiliferous slates of Lee, Rockham, Mor- 

 tehoe, Lundy, AVinsford, and the southern flanks of the Exmore, 

 * Always occurring in the slates. 



