254 R. H. Rastall — Minerals of Barrington Bone-bed. 



containing a good many small flints and pebbles of hard Chalk. 

 After passing through a sieve to remove the larger fragments, the 

 material was washed with water. After prolonged washing the 

 white chalky mud was removed and the residue was found to be 

 a clean white sand, consisting of approximately equal parts of 

 colourless quartz and white calcareous matter, chiefly Chalk in small 

 rounded grains. There were also abundant white prismatic structures, 

 Apparently including both prisms from the shells of Inoceramus and 

 spines of Echinoids. Red, brown and black grains constitute only 

 a small proportion of the whole, while glauconite is also to be seen 

 occasionally. 



With dilute acid the effervescence was naturally very copious, and 

 the insoluble residue was a notably white sand. The heavy con- 

 stituents of the sand were then roughly concentrated by panning, 

 and finally separated in bromoforra in the usual way. 



The principal minerals noted in the ultimate residue were as 

 follows : garnet, abundant, in angular, subangular and rounded 

 grains, often very strange shapes, either colourless, pink, or pale 

 brown ; tourmaline, common, in round grains or less commonly 

 idiomorphic crystals, generally brown ; kj-anite, rather abundant, in 

 angular fragments or rounded grains ; staurolite, in rounded grains, 

 a rather unusual circumstance; muscovite, in small quantity, chiefly 

 in minute flakes. Other less common transparent minerals were green 

 and blue hornblende, deep-red rutile and yellowish-green epidote. 

 Among the opaque constituents the most abundant were pale-brown 

 rounded grains of indeterminable nature, together with a smaller 

 quantity of magnetite. The significance of this assemblage of 

 minerals and their probable source will be discussed in the concluding 

 section. 



2, This was a small sample collected from near the middle of the 

 bed. In general character it was much like the last, and the residue 

 of white sand was almost identical in appearance. The chief minerals 

 found in the rather scanty heavy residue from bromoform were as 

 follows : garnet occurs in grains rather larger than the rest, 

 colourless, pink or brown, and of a great variety of shapes, often very 

 angular, though some are distinctly rounded. Hornblende is common, 

 chiefly of the ordinary green variety, though some grains have a blue 

 tinge. Staurolite and kyanite are rather abundant in fairly large 

 grains, although tourmaline is not very common. Among other 

 transparent constituents rutile and epidote are the most notable, 

 zircon being quite rare. Muscovite also occurs in small flat flakes. 

 When examined by reflected light magnetite is seen to be very 

 common, and there are also opaque white and brown grains. The 

 general form of the mineral grains shows much variation, some being 

 conspicuously rounded while others are just as notably angular. It 

 is probable that the very round grains have been obtained in that 

 state from some older formation. 



3. This specimen is of special interest, since it represents the 

 lowest part of the deposit, the actual bed in wliich the bones are found. 

 It is a white marly substance, soft and rather plastic when fresh and 

 moist, but when dried setting into a hard mass. This, however, falls 



