250 PROCEEDIN-GS OF THE GEOLOGICAL SOCIETY. [Apr. 3, 



as to whether these beds are palaeontologically separable from the 

 Tealby series. 



Lastly, I have shown that, in Lincolnshire at least, the occur- 

 rence of beds of a red colour in the Cretaceous series is by no means 

 a unique phenomenon. The explanation of the reactions by which 

 the colouring-matter in these cases, anhydrous peroxide of iron, has 

 been produced, offers an interesting problem to the chemical geolo- 

 gist — one which he can only hope to solve by combining extensive 

 observation in the field with minute research in the laboratory. 

 The explanation, when found, will probably embrace other cases of 

 the occurrence of red limestone, such as those of Liferior Oolite age 

 at Bredon Hill*, and those of Devonian age in Devonshire, with 

 others which wiU doubtless occur to geologists f. Regretting that I 

 am at present unable to carry out my design of supplementing the 

 present paper by a series of careful analyses of the various red beds 

 described in it, I add the following general observations, which may 

 be of use to any one investigating the subject : — The ordinary white 

 chalk of Lincolnshire, when exposed to a moderate degree of heat, as 

 in the sides of lime-kilns, becomes pink or red ; while the red chalk 

 of Louth, as well as that of the Hunstanton series, makes a perfectly 

 white lime ; indeed the red beds are preferred by the lime-burners to 

 the white ones. The explanation of these facts is probably as 

 follows : — in the first case the small quantity of hydrous or brown 

 peroxide of iron is dehydrated, and converted into the intensely 

 colouring red oxide ; perhaps also by a slow oxidizing process the 

 minute grains of silicate of iron are decomposed : in the latter case 

 an exactly opposite action takes place, the peroxide of iron is reduced 

 (probably by carbonic oxide) to the state of protoxide, and, uniting 

 with the sihca, forms silicate of the protoxide of iron, which is pale- 

 green, and of extremely feeble colouring-power. The existence of 

 large quantities of silica in the Lower Chalk and Hunstanton beds is 

 shown by the fact that, when used for hme-burning, great care is 

 required to prevent the heat from rising to too high a degree, in 

 which case the whole contents of the kiln would run together in 

 consequence of the formation of fusible silicates. 



VII. Notes on some oe the Fossils. 

 1. Pecten ciifCTiJS, ^ow.= p. circularis, Goldt=P. crassitesta, Eom. 



This species was originally described by Sowerby from two speci- 

 mens, one of which was obtained from Lincolnshire, and the other 

 from the drift of Suffolk ; by him they were erroneously referred to 

 the inferior Oohte, on account of the resemblance of their matrix to 

 the " ironshot oolite " of that formation. Although both Mr. Lee 

 and Prof. Phillips correctly quote this species, and Romer himself, 

 in 1841 $, cancelled his own name in favour of that of Sowerby, other 

 palaeontologists have constantly applied the latter to two other quite 



* Strickland's Collected Works, p. 81. 



t It may be of interest to mention that beds of red limestone occur in the 

 Oolite near Lincoln. X Verst. Nord. Kreid. Geb. p, 70. 



