Correspondence — J. T. Stobbs. 335 



have been sunk through and bored, perhaps in a hundred places, 

 whilst scores of mining engineers, inspectors, colliery managers 

 (whose success depends largely on their detailed knowledge of the 

 strata of their mines) are and have been engaged in the exploitation 

 of these seams, and we may presume that the sequence must be fairly 

 Avell known lithologically. And so far as one can gather from his 

 paper, it is solely upon lithological evidence Dr. Woolacott bases 

 his conclusion that the boreholes lie describes were in the Ganister 

 Series. The generic names of the fossil plants he gives are quite 

 useless in Coal-measure stratigraphy, and his quaint note that 

 " no trace of any characteristic fossil [italics are mine] such as 

 Avicidopecten papyraceus was found" leads one to infer that he has 

 not followed recent palseontological work in the Coal-measures, or he 

 would not place so much reliance for zoning purposes on the discovery 

 of Pterinopecten papyraceus. It is to be hoped that Dr. "Woolacott is- 

 in possession of other evidence of higher diagnostic value to warrant 

 his opinion of the horizon reached by the boreholes. A perusal of 

 this paper has suggested a fair reason for the disinclination of some 

 mining people to seek the assistance of the geologists. 



In the May issue of the Geological Magazine (pp. 203-211) 

 Drs. Trechmann and Woolacott were constrained " to put definitely 

 on record" the fact of the occurrence of the zone of Anthracoviya- 

 phillipsi in the Coal-measures of Durham. They omitted to mention 

 that this had already been done in the following papers, viz. 

 Geol. Mag., 1905, pp. 536-7, and Trans. Inst. Min. Engineers,, 

 vol. xxx, pp. 453-4, 1906, where the stratigraphical significance of 

 the discovery was clearly stated. 



J". T. Stobbs. 



Stoke-on-Trent. 

 May 21, 1919. 



PRODUCTUS HUMEBOSUS IN DOVE DALE. 



Sir, — I had the good fortune recently to meet with two specimens- 

 of Productus humerosus (P. sublcevis) in Dove Dale (Derbyshire). 

 This discovery seems worthy of record in point of view of the fact 

 that hitherto the species has only been recorded for the Midland 

 area from Caldon Low (Staffs). The Dove Dale examples occurred 

 in a loose limestone block on the screes immediately below Reynard's 

 Cave. In general form the specimens are strongly convex, narrow, 

 and smooth, resembling the narrow form from Caldon Low described 

 in this Magazine for February, 1919, p. 64. The matrix, however, 

 is quite unlike that of the Caldon examples. 



J. "Wilfrid Jackson. 



Manchester Museum. 

 May 22, 1919. 



MOUSTERIAN FLAKE-IMPLEMENTS. 

 Sir, — I notice that in my letter published in the Geological 

 Magazine for May, p. 240, I am made to speak of "the earlier 

 Palaeolithic 'cave' implements", and of "a normal Chellean or 



