TEE CAEBONIFEKOUS-LIMESTONE SERIES AT CLIFTON. 193 



of Foramiuifera, and a quantity of spicules of sponges (Plate VIII. 

 fig. 5). 



jN'o. 16. Detrital quartz in quantity ; small fragments of chalce- 

 donic silica ; chalcedonic spherical objects, measuring from '002 to 

 •004 of an inch in diameter (Plate VIII. fig. 6). 



No. 18. Small pieces of amorphous and chalcedonic silica ; detrital 

 quartz-grains averaging about "002 of an inch in diameter, and some 

 tourmaline. 



'No. 19. Detrital quartz and tourmaline ; pieces of amorphous and 

 chalcedonic silica ; micro-crystals, some of which measure -003 x 

 •004 of an inch. 



Uppee Limestone. 



No. 1. Detrital quartz with secondary silica deposited on the 

 surfaces, and a few perfect crystals. 



No. 2. Fragments of chalcedonic silica, among which spicules of 

 sponges were detected, dark siliceous objects, some of them casts or 

 pseudomorphs ; pyrites, detrital quartz, and tourmaline. 



Xo. 3. Detrital quartz ; micro-crystals with detrital quartz- 

 nuclei; chalcedonic silica and tourmaline. 



No. 4. Oolitic limestone ; the residue contains detrital quartz, 

 averaging about •OOS of an inch in diam.eter. 



No. 5. Oolitic limestone ; with residue consisting of detrital 

 quartz, chalcedonic silica, siliceous pseudomorphs or casts, and a 

 quantity of pyrites which also appear to be pseudomorphs. 



Review oe the Residues. 



The residues derived from the Lower Limestone Shales consist 

 mostly of detrital quartz, occasionally associated with amorphous and 

 chalcedonic silica, some of which is in the form of casts and pseudo- 

 morphs of organisms. With the detrital quartz are fragments of 

 tourmaline, zircon, and felspar. 



The Black-Eock limestone yields residues made up of a large 

 proportion of detrital quartz, distinguished from the same residue 

 in the Lower Limestone Shales by a slight secondary deposit of silica 

 on the surfaces ; and in some cases complete crystals have been 

 so formed with an original quartz-grain as a nucleus. Amorphous 

 and chalcedonic silica is more plentiful than in the limestone 

 below ; and the minerals tourmaline, zircon, and pyrites are fre- 

 quently met with. 



Coming to the base of the Middle Limestones, that is to the 

 oolitic beds, the residue is made up of rolled detrital quartz-grains 

 and a few fragments of felspar and tourmaline. Above this 

 horizon the residue undergoes a change, and becomes more typical 

 of the Middle Limestones. Detrital quartz-grains occur, but not to 

 the same extent as in the residues previously examined ; on the 

 other hand, the proportion of chalcedonic silica has increased. The 

 residues of the Middle Limestones mav be said to consist of detrital 



