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XV. — On the Lamellibranch and G-asteropod Fauna found in the Millstone Grit of 

 Scotland. By Wheelton Hind, M.D., B.S., F.E.C.S., F.G.S. Communicated by 

 Dr J. Horne, F.R.S. (With Two Plates.) 



(MS. received February 12, 1908. Read March 16, 1908. Issued separately September 2, 1908.) 



PART I. 



Introduction. 



During the revision of the Midlothian coalfield by the Geological Survey, special 

 attention was directed to the plant remains occurring in the Millstone Grit, with the 

 view of obtaining evidence bearing on the probable boundary line between the Upper 

 and Lower Carboniferous rocks. Mr Tait collected a number of plants from certain 

 horizons in this division of the Carboniferous system, which were submitted to Mr 

 Kidston, F.R.S. , for determination. Those from the lower part of the Millstone Grit 

 were regarded by Mr Kidston as belonging to the Lower Carboniferous flora, and those 

 from the upper portion, to the Upper Carboniferous flora. While carrying on his work 

 in the field, Mr Tait found certain fossiliferous bands in the basal portion of the Mill- 

 stone Grit, charged with lamellibranchs, brachiopods, and other marine organisms, and 

 associated with Lower Carboniferous species of plants. These observations were of 

 service in tracing the base line of the Upper Carboniferous rocks round a large part of 

 the Midlothian basin. It ought to be clearly understood, however, that this boundary 

 line is based solely on the evidence supplied by the plants and fishes as determined by 

 Mr Kidston and Dr Traquair respectively. 



When the revision of the Midlothian area was completed, certain sections of the 

 Millstone Grit in the counties of Linlithgow, Lanark, and Stirling were examined by 

 Mr Tait, to see if they might furnish confirmatory evidence of the boundary line 

 adopted in Midlothian. Owing to the economic importance of the fireclays in this 

 division in Lanarkshire, which has led to extensive boring operations, the sequence of 

 the lower part of the strata in that district is now well known. In the basal portion 

 there are fossiliferous bands containing marine organisms just as in Midlothian. 

 Though Lower Carboniferous plants have not been found in this division in the districts 

 of Glenboig, Castlecary, or Torwood Glen, yet they have been met with in beds a little 

 above the base of the Millstone Grit at Glasgow, and Upper Carboniferous plants have 

 been obtained in the upper part of this division at Castlecary. It seems reasonable to 

 infer, therefore, that the lower part of the Millstone Grit in the counties of Lanark, 

 Linlithgow, and Stirling is on the same stratigraphical horizon as the basal portion in 

 Midlothian with its marine bands and Lower Carboniferous flora. 



TRANS. ROY. SOC. EDIN., VOL. XLVI. PART II. (NO. 15). 51 



