030 EDWARD HULL ON THE CLASSIFICATION 



that the coniuiunity of 28 species is a fact which strongly corrobo- 

 rates the views here suggested*. 



It should be recollected also that, over the north of England and 

 the borders of Scotland, land and shallow-sea conditions prevailed 

 during the earlier Carboniferous stages. This accounts for those 

 changes in the limestone series that have been pointed out by 

 Phillips and Murchison, and more recently by Mr. Lebour. Such 

 changes would necessarily be accompanied by the disappearance of 

 various forms which nourished in the deeper seas of Central England, 

 and the appearance of others more adapted to shallow water. 



Part Y. 



Continental Equivalents. 



A. Stage E — Lower Coal-measures. 



That the great mass of the Coal-measures of Belgium, Erance, 

 Rhenish Prussia, and North Germany are characterized by shells of 

 recognized freshwater or lacustrine habitats is well known from the 

 writings of continental geologists. Thus, we learn from the authors 

 of ' Die Steinkohlen Deutschlands ' that the Coal-measures of Saxony 

 and Westphalia are characterized by the prevalence of such forms as 

 Unto, Anodonta, Cyrcna, Cyelas, Dreissena, Cardinia (Anthracosia), 

 and Planorbisf. At the same time one or two bands of marine shells 

 occur amongst this great mass of lacustrine or estuarine strata, in a 

 manner similar to that which 1 have described above as being present 

 in Forth Staffordshire and at Ashton-under-Lyne. Thus, Herr E. 

 Ludwig has recognized Goniatites and Aviculopecten in the Coal- 

 formation of Westphalia both near the base of the formation and at 

 a higher horizon J. It cannGt be doubted that the former position 

 is that of the " Gannister Beds " (Stage E). 



The occurrence of a marine band at the base of the Coal-formation, 

 and in the position of the Gannister Beds of England is now fully 

 established by the labours of several observers, particularly Prof. P. 

 Romer, of Breslau§, and M. Charles Barrois, of Lille ||, and of Prof. 



* On communicating to my colleague, Professor Geikie, Director of the Geo- 

 logical Survey of Scotland, the views above expressed regarding the represen- 

 tative beds on each side of the border below the Millstone Grit, he replies (in 

 letter dated 24th Nov. 1876) that the correlation is a natural and probable one, 

 and that for several years the Scottish Surveyors have always believed the so- 

 called "' Carboniferous-Limestone series " to represent generally all the English 

 f-eries between the Millstone Grit and the base of the Scaur Limestone. At the 

 same time the survey of the border districts had not sufficiently far advanced to 

 warrant the adoption of the English names of subdivisions. 



t Herren Geinitz, Fleck, and Hartig. Band I. pp. 107-8 and 109. 



j Von Meyer and Dunker, ' Paheontographica,' viii. pp. 31-38. 



§ " Ueber eine marine Conchylien-Fauna im produktiven Steinkohlengebirge 

 Oberschlesiens," Zeitschr. d. deuts. geolog. Gesellsc-h. 1863. 



i| " Sur la faune marine du terrain houiller, &c," Bulletin de la Soc. Geolog. de 

 France, 3 e ser. t. ii. p. 223. 



