272 ME. H. B. BEADY ON SACCAMMINA CAETEEI. 



deal altered by heat, but portions at least of it are entirely com- 

 posed of tbe same fossil remains. 



The Elf hills bed appears again on the banks of the Wansbeck 

 above Wallington Hall, where it has more or less of the same 

 spheroidal structure, determined by the presence of its charac- 

 teristic fossil. 



As the "four-fathom limestone" traverses the Alston Moor 

 district, it can scarcely be doubted that the specimens originally 

 found by Mr. Charles Moore amongst other Foraminifera, asso- 

 ciated with the mineral veins of the higher part of Weardale, 

 have been derived from it ; but hitherto no fossil similar in cha- 

 racter to those of the Northumberland bed has been discovered, 

 though carefully sought for by'my friend Dr. Savage, of Nent- 

 head, who is thoroughly conversant with the geology of that 

 region. 



It seemed desirable to compare the Elfhills rock with other 

 spheroidal and concretionary limestones of palaeozoic age ; and 

 for the means of doing so I am indebted to the kindness of Mr. 

 Etheridge, the palaeontologist to the Geological Survey, who has 

 furnished me with a number of specimens of such limestones, 

 some of them Carboniferous, others from the Wenlock and Bala 

 beds. In each of the specimens there is some prima-facie re- 

 semblance to the Elfhills rock, and in one or two the similarity 

 is so striking that the naked eye is hardly sufficient to discern 

 the differences that in point of fact exist between them and it. 

 By means of transparent sections and a good microscope, the 

 true structure is readily made out ; and in all the specimens sent 

 by Mr. Etheridge it is essentially the same. They are composed 

 of laminated spheres of carbonate of lime, formed by the common 

 process of spherical coalescence, and that their physical peculia- 

 rities are in no way due to organic remains may be asserted 

 with certainty in every instance. 



Chemical. — Although the Elfhills limestone is as compact as 

 many varieties of marble, considerable difficulty is experienced 

 in obtaining a polished surface by grinding, owing to the dif- 

 ferent degrees of hardness of its constituents. The matrix is 



