688 DR RAMSAY H. TRAQTTAIR ON THE DISTRIBUTION OF FOSSIL FISH-REMAINS 



however, different in Scotland, where the strata below the Millstone Grit, though con- 

 taining intercalated beds of marine limestone, are largely similar to those of the over- 

 lying Coal Measures in their lithological character, and in the fades of their imbedded 

 organic remains. This is a matter of great importance in connection with the question 

 of Life-Zones in the Carboniferous system which has for some time back been engaging 

 the attention of British geologists. Mr Kidston * has pointed out the dissimilarities 

 between the Upper and Lower Carboniferous land flora in Great Britain, and I have 

 on more than one occasion t drawn attention to the fact that different assemblages of 

 estuarine fishes characterise the two great divisions of the strata of this period in our 

 island. 



Before proceeding with the enumeration of genera and species from the various 

 horizons, it is, however, necessary to lay before the reader a general view of the relations 

 of the strata of the Carboniferous area of the district in question, namely, that embraced 

 in Sheet 32 of the Ordnance and Geological Surveys of Scotland. For that purpose I 

 applied to the Director of the Geological Survey in Edinburgh, and received from him 

 the general section of the Carboniferous rocks of the Lothians given in Plate I., and 

 which was drawn up by Dr B. N. Peach, F.R.S. 



One thing which strikes the eye at the first glance is the small comparative thick- 

 ness of the Upper Carboniferous series in this section, the Coal Measures with the Mill- 

 stone Grit occupying only about 1500 feet, while the subjacent Lower Carboniferous 

 attains a thickness of at least 7000 feet, and is probably still thicker in its lower part 

 than here represented. 



The Lower Carboniferous division commences above with the so-called " Carbonifer- 

 ous Limestone Series," which, however, consists principally of sandstones, shales, fire- 

 clays, ironstones, and coal-seams, some of the latter being of great economic value. 

 Intercalated among these towards the top, and again towards the bottom of the series, 

 are beds of marine limestone ; hence the threefold subdivision into Upper Limestone, 

 Edge Coals, and Lower Limestones — the name of the middle group being derived from 

 the circumstance that at Drum and Niddrie, in Midlothian, these strata are tilted up on 

 " edge," so as in fact to be nearly vertical. 



Below the Carboniferous Limestone Series comes the thickest part of the Lower 

 Carboniferous division in this region ; namely, the " Calciferous Sandstones " of 

 Maclaren, the subordinate members of which are noted in the section, and will be 

 dealt with in succession further on. This series is in the Edinburgh district character- 

 ised by a rarity of " marine " beds, the principal limestone, that of Burdiehouse, being 

 also of estuarine origin, like the sandstones, shales, and ironstones which constitute the 

 mass of the rocks here included. Most geologists are agreed that the Calciferous Sand- 

 stones of Scotland represent the lower portion of the " Carboniferous Limestone " of 

 England and Ireland, though deposited under very different conditions. 



* Proc. Roy. Phys. Soc. Edin., vol. xii. 1893, p. 190 et seq. 



t hoc. cit., p. 386, 387. Also, Geol. Mag. (3), vol. i. 1884, p. 121. 







