E. Wethered — Organisms in Carboniferous Limestone. 537 



The foregoing analysis shows the limestone to be dolomitized, the 

 carbonate of magnesia being as high as 37 per cent. Of this I shall 

 treat further under the head of chemistry. 



The Upper Limestone Series. 



This series consists of two varieties of limestone locally termed 

 the " Crease " and " Whitehead." The former occupies the lower 

 horizon of the two. 



The Crease (PL XV. Fig. 9). — The samples which I have examined 

 show an unusually coarse structure due to the size of the calcareous 

 fragments of which the limestone is made up. The origin of these 

 calcareous fragments is somewhat obscure, but I have detected among 

 them undoubted remains of Crinoids. The grains are closely com- 

 pressed, reminding one of the structure of arenaceous grits ; the 

 rock is, indeed, a calcareous grit. 



The " Whitehead " Limestone. — The " Whitehead " follows the 

 " Crease," and is represented by an interesting series of beds from 

 which I have selected the following as typical. 



No. 1 (PI. XV. Fig. 11). — Oolitic limestone, from a thickness of 

 about forty feet. The granules measuring from -007 to *018 of an inch 

 in diameter. The nuclei are generally destroyed, leaving an open 

 space. The spaces between the granules are often wide and are 

 filled with calcite. 



No. 2. — A concretionary limestone from a bed three feet thick. 

 Contains the valves of Ostracoda, spines of Productus and angular 

 grains of quartz. There are also present circular rings as .large as 

 •005 of an inch in diameter, and are a conspicuous feature in the 

 rock. 



No. 3. — From a bed made up of concretionary nodules, as large as 

 an inch in diameter, and calcareous sand. Microscopic sections of 

 the nodules reveal the remains of a variety of organisms, but all 

 badly preserved. 



No. 4. — This is a very interesting bed, and makes a beautiful object 

 under the microscope (PI. XV. Fig. 12). The rock is made up of the 

 remains of a spiral shell, of Foraminifera, Ostracoda, Polyzoa, and 

 obscure calcareous fragments, the whole being cemented together by 

 clear calcite. 



No. 5 (PI. XV. Fig. 10). — A peculiarly white limestone, which 

 gave the following analysis : — 



Insoluble residue (sand) 









.. 2.95 



Organic matter 









6-94 



Water 









1-40 



Carbonate of Lime 









.. 85-56 



Carbonate of Iron 









•46 



Soluble Silica 









•01 



Carbonate of Magnesia 

 Alkalies 









•84 

 1'06 



Pbosphate and Sulphate 



of Lime, 



and 



loss ... 



•78 



100-00 

 Sections of the limestone show it to be largely made up of the 



