G4I EDWARD HULL ON THE CLASSIFICATION 



(c) Occasional Marine Beds in Stage E. 



That the ocean-waters were not far distant from the British and 

 European areas during the formation of the Middle and Upper Coal- 

 measures is proved by the appearance at rare intervals of bands of 

 truly marine shells. Such are those which occur above the " Bay 

 Coal" and the " Gin-mine Coal" in North Staffordshire*, that in 

 the banks of the river Tame at Ashton-under-Lynef , and that of the 

 " Chance Pennystone" of Coalbrook Dale. But it should be observed 

 that the species in these bands are sometimes different from those in 

 the Gannister beds, most of which have descended from the Carboni- 

 ferous Limestone. Thus, out of about 29 species determined by 

 Salter from the Lower Coal-measures (Stage E) of South "Wales J, all 

 but five, viz. Avicidopecten gentilis (Sow.), A. scalaris (Sow.), Myalina 

 triangularis (Sow.), Discites falcatus (Sow.), and Nautilus concavus 

 (Sow.), have been recognized in the Carboniferous Limestone. The 

 species from the same stage in Coalbrook Dale and South Staffordshire 

 are similarly related to those of the Mountain Limestone ; the ex- 

 ceptions to identity are probably owing to insufficient knowledge of 

 the Lower-Carboniferous fauna. 



On the other hand, if we compare the species from the accidental 

 marine bands which occur in the Middle Measures (Stage E) we find 

 them to be mostly peculiar to that horizon. Thus, out of about ten 

 species from the marine band at Ashton-under-Lyne only one was 

 considered by Salter to be identical with a form from the Gannister 

 beds. Of this remarkable group Mr. Salter has observed : — " A 

 special notice should be given of this marine band, containing as it 

 does a small peculiar fauna, comparable with that of the Lower Coal- 

 measures of Shropshire, but yet wholly distinct. It is true the com- 

 mon marine shell, Avicidopecten papyraceus, occurs in this remark- 

 able band ; but even this is dwarfed, and, except this species, the 

 fossil contents are wholly different from those of the Gannister beds 

 and those of the beds among which they occur"§. These species, 

 nevertheless, may be regarded as the representatives of the fauna 

 living in the adjoining seas during the deposition of the strata of the 

 Middle and Upper Coal-measures, and as such differing to some ex- 

 tent from that of Stage E. It is only thus by accident (as it were) 

 that we obtain a view of the characters of the marine fauna during 

 the long stage of the great coal-growth. 



(d) Present Mode of Classification Objectionable. 



With such palseontological evidence before us, it has long seemed 

 to me that the generally received system of classification, by which 

 the whole Carboniferous series is divided into only two great divi- 

 sions, does not express the real relations of the different members to 

 each other. The stages above the Mountain Limestone, including 



'"■ Discovered by Mr. John Ward, of Longton. 

 t Discovered by Prof. A. II. Green. 



\ Rosser vein, a seam above the true Millstone Grit, ' Iron-ores of Great 

 Britain,' part iii. p. 221. 



§ ' Geology of Oldham, &?.' (Mem. Geol. Survey), p. 64. 



