OF THE CARBONIFEROUS SERIES. 649 



This classification rather closely approaches the one here suggested. 



In the 3rd edition of the ' Coal-fields of Great Britain,' having 

 recognized, though not so fully as at present, the palaeontological 

 connexion between the Gannister Beds (Stage E) and the Mountain 

 Limestone, I placed all the beds from this formation downwards 

 inclusive in the "Lower Carboniferous" division. Though this 

 arrangement is, from my point of view, preferable to that which 

 places all the beds above the Limestone in the Upper Carboniferous 

 division, it is open to the objection of not sufficiently recognizing 

 petrological characters and affinities. 



The conflicting views amongst authors above noticed is to be 

 attributed to the want of some clear principle upon which to deter- 

 mine the relationshijDS of the various members of the Carboniferous 

 series to each other. The palaeontological differences between the 

 Gannister Beds and the Coal-measures seem to offer a good basis for 

 drawing a divisional line at this horizon ; while the petrological 

 differences between the Carboniferous Limestone and the succeeding 

 stages, together with the great destruction of coralline, crinoidal, and 

 molluscan life at the close of the former stage, afford sufficient grounds 

 for drawing another line of division at this lower horizon, — thus con- 

 stituting a middle Carboniferous group, the beds of which are closely 

 related in mineral and palaeontological characters. 



(e) Proposed Classification. 



In order, therefore, to give the affinities and differences in the 

 Carboniferous beds due recognition, it seems desirable to adopt 

 a threefold arrangement, constituting a middle group differing 

 from the lower in mineral characters, and from the upper in the 

 characters of the prevalent molluscan fauna ; and with this object 

 the arrangement shown in Table I. p. 640, seems to me the most 

 natural that can be adopted. 



In speaking of the main divisions as " essentially marine," 

 " essentially lacustrine," &c, I wish those terms to be understood 

 as representing the prevalent conditions, which admit of exceptions, 

 as in the case of the Lower Carboniferous group, which, though 

 essentially marine, contains in Scotland marginal representatives of 

 the period which are estuarine and lacustrine in character. 



(/) Summary of Conclusions. 



From the above considerations it is to be inferred that the Gan- 

 nister Beds (Stage E) should be dissociated from the main mass of 

 the coal-measures above, and grouped with the formations below : — 



First. Because Stage E is essentially of marine origin, while 

 Stages F and G are essentially estuarine and lacustrine. (See 

 Table III.). 



Secondly. Because the few marine species found in Stages F and 

 G are for the most part specifically different from those in Stage E. 

 (See Table IV.) 



Thirdly. Because of local breaks in stratification between Stages 

 E and F, concurrent with the palaaontological break*. 



* An illustration of Professor Ramsay's views, as expressed in his Presidential 



