496 E. A. Newell Arber — Culm-measures of Exeter District. 



in the neighbourhood of Exeter. He treats the whole flora and fauna 

 as if it belonged to one division of the stratigraphical series, whereas 

 the specimens from some localities are of Lower, and those from others 

 of Upper Carboniferous age. I imagine that if the author had collected 

 fossils around May Hill, in Gloucestershire, where there is a series of 

 sediments ranging from the Silurian to the Jurassic and including the 

 Carboniferous, he would have paid some attention to the stratigraphv 

 of the area, and would not have treated the whole of his collection as 

 if it belonged to one formation or a particular subdivision of a single 

 formation, as he has done in this case. 



In this connexion it may be well to point out once again that before 

 1840 Sedgwick & Murchison 1 had realized that both the Lower and 

 Upper Carboniferous formations are represented in the Devonshire 

 syncline. The rocks belonging to the Lower series they called the 

 Lower Culm-measures, those to the Upper, the Upper Culm-measures. 

 1 have also adopted this twofold division in my papers on the Culm- 

 measures of North and West Devon, 2 though, as 1 then pointed out, 

 the term Culm-measures is misleading and unnecessary, and is 

 therefore best dropped. 3 



The Lower Carboniferousrocks (Lower Culm-measures) of Devonshire 

 are quite distinct lithologically from those belonging to the Upper 

 Carboniferous, and where a clear section exists there should be little 

 possibility of mistaking the one for the other. I am not acquainted 

 with the Culm-measures near Exeter in the south-east corner of the 

 basin in detail, but in the south-west corner in North Cornwall I have 

 studied them carefully, and they will be found described in my Coast 

 Scenery of North Devon, recently published. There the lithological 

 differences between the Upper and Lower Culm-measures are certainly 

 marked. But I may point out that it has been known for many years 

 past that both Lower and Upper Culm-measures occur around Exeter. 

 Lower Culm-measures are indicated to the west and south-west of 

 Exeter on the sketch-map accompanying Messrs. Hinde & Eox's 

 well-known paper on the Kadiolarian rocks of Devon. 4 The relations 

 of the Lower to the Upper Culm-measures in this district are also 

 shown very clearly in the admirable map accompanying Mr. Ussher's 

 paper 5 on the Culm-measure types of Great Britain, published in 1901. 

 It is true that in the revised Survey map (Sheets 325 and 339) of the 

 Exeter district the two series are not distinguished f roru one another, 

 but in the accompanying memoir Mr. Ussher 6 has clearly discriminated 

 between them. 



1 Sedgwick & Murchison, Trans. Geol. Soc, ser. u.vol. v, pp. 682, 684, 1840. 



2 Arber, Phil. Trans. Eoy. Soc. London, ser. B, vol. cxcvii, p. 291, 1904. 



3 The term ' Culm ', as used by Mr. Collins in the title of his paper, is even 

 more objectionable. It is an old West of England word for the slack of an 

 anthracitic coal. As used by geologists, it is apparently a translation of the 

 German ' Kulm ', which itself originated on the Continent under a misconception 

 of the nature of the Culm-measures of Sedgwick & Murchison in Devon and 

 Cornwall. 



4 Hinde & Fox, Quart. Journ. Geol. Soc, vol. li, p. 609, pi. xxiii, 1895. 



5 Ussher, Trans. Inst. Min. Engineers, vol. xx, p. 360, pi. xvi, 1901. 



6 Ussher, The Geology of the Country around Exeter (Mem. Geol. Surv.), 

 ch. ii, 1902. 



