300 EEOCEEDIXGS OE THE GEOLOGICAL SOCIETY. [Feb. 5, 



Approximate, Analysis of tlic Synchronous Distribution of Fossils. 



The foregoing Lists give the following results : — 



Number of Great-Oolite forms 230 



,, „ Lincolnshire-Limestone forms 315 



„ „ Northampton-Sand forms 250 



Total 795 



Of these— 



135 are common to the Northampton Sand and the Lincoln- 

 shire Limestone. 

 70 to the Lincolnshire Limestone and Great Oolite. 

 46 to the Great Oolite and Northampton Sand. 

 43 to all three formations. 

 If, from the number of forms common to the Northampton Sand 

 ahd the Lincolnshire Limestone, and from the number common to 

 the Lincolnshire Limestone and the Great Oolite, respectively, be 

 deducted the number of forms common to all three formations (as 

 having no significance in determining their comparative affinity), 

 there will remain : — 



92 forms common only to the Northampton Sand and the 



Lincolnshire Limestone. 

 27 forms common only to the Lincolnshire Limestone and the 

 Great Oolite. 

 Many fossils of the Lincolnshire Limestone and Northampton 

 Sand have yet to be identified and described, which ultimately will 

 considerably swell the foregoing numbers as regards those for- 

 mations. 



EXPLANATION OF PLATES IX. AND X. 



Plate IX. 



Map of the author's route and of the southern portion of the Lincolnshire 

 Limestone. * * Points of thinning-out of the Lincolnshire Limestone. For 

 section see PI. X. fig. 2. , 



Plate X. 



Fig. 1. Diagrammatic section across the Welland Valley at Stamford. 

 Fig. 2. Generalized section from the Talley of the Welland to that of the 

 Nene, illustrating the thinning-out of the Lincolnshire Limestone. 



DlSCESSIO^. 



Mr. Etheeidge expressed his obligation to the author for his 

 paper, and for the remarkable collection of fossils he had exhibited. 

 The ground over which he had worked was one the features of which 

 had required a great amount of well-directed labour to decipher. He 

 considered, however, that Mr. Sharp and Mr. Judd had settled the 

 question of the sequence of these rocks, and their relation to the 

 Oolitic beds of Yorkshire to the north, and Gloucestershire to the 

 west. The importance of the determination of the position of a bed 

 of such commercial value as the Northampton Sand could hardly be 

 overestimated ; and it was to Mr. Judd and to the author that this 



