174 CARBONIFEROUS LAMELLIBRANCHIATA. 



Carboniferous Limestone being only represented by some few feet of shales at 

 Fremington ; unless the Pilton beds are its homotaxial equivalent. 



The Pendleside Series thins out rapidly to the south of Derbyshire, and is only 

 represented by a few feet in Leicestershire and Shropshire. Still further south, 

 I consider that the Bishopton beds in South Wales and the Lower Culm Series of 

 Devonshire are the homotaxial equivalents of the Pendleside Series of the Midlands. 

 The lithological similarity of the series in Devonshire, and especially the peculiar 

 fauna of the Lower Culm, agree so markedly with the characters of the Pendleside 

 Series that one cannot be blind to the evidence. Moreover, the Lower Culm is 

 overlaid by grit beds, which are in turn overlaid by a soft shales with bullions at 

 Instow containing — 



Pterinopecten papyraceus, Gastrioceras carbonarium, 



Posidoniella Isevis, Dimorphoceras Gilbert soni, 



Gastrioceras Listeri, Orthoceras, sp. — 



a fauna which is abundant in the Lower Coal Measures of Lancashire and the 

 Midlands; and at Robert's Quarry, near Bideford, immediately above beds 

 containing a fairly rich and typical Coal Measure flora, is a band of fawn-coloured, 

 iron-stained, shale with Carbonicola acuta, a characteristic shell of the middle portion 

 of the Coal Measures, so that one may safely infer that the Culm Measures of Devon- 

 shire represent the Carboniferous sequence of the Midlands, minus the massif of 

 Carboniferous Limestone. 



Eastwards the beds thin out, but at Clavier, near Dinant in Belgium, beds of 

 similar lithological character to the Pendleside Series, with the typical fauna, are 

 found. Still further east, at Magdeburg and Herborn, the Culm of Germany has the 

 peculiar fauna which characterises the Lower Culm and Pendleside Series in 

 England. 



Although beds containing the same marine fossils, which are found at much 

 lower horizons, occur here and there throughout the Upper Carboniferous Series, 

 the great faunal break occurs at the base of the Pendleside Series. A new set of 

 Mollusca come in at this horizon for the first time, and by far the larger number of 

 Lower Carboniferous organisms totally disappear. Leaving the Brachiopoda out 

 of the list, because it is doubtful if any forms are confined to the Upper Car- 

 boniferous Series, more than three fifths of the fauna of the Pendleside Series are 

 new, i. e. they do not occur at horizons lower down. Curiously enough, it would 

 appear that the faunal change took place before the floral, and a lower Car- 

 boniferous flora is thus found in beds with an upper Carboniferous fauna. The 

 change in the fish faunas, however, corresponds to that of the Mollusca. Hence 

 palceobotanists would subdivide the Carboniferous Series into an upper and lower 

 at a somewhat higher horizon than zoologists. 



The important point in Carboniferous classification is to recognise that the term 



