Vol. 69.] TWO DEEP BORINGS AX CALVERT STATION. 319 



oolitic limestones also were undergoing denudation at no great 

 distance. This fits in well with the repeated non-sequences of 

 which the stratigraphy gives evidence. 



Oolitic limestone at 197 and 203 feet (Chipping-Xorton 

 Limestone). — These are quite typical oolitic limestones, the only 

 ones in regard to which it can be confidently asserted that the 

 majority of the grains are of contemporaneous origin. The two 

 beds are separated by very sand}' limestones, in which, however, 

 there are also abundant oolite-grains. 



Even these beautifully oolitic rocks give the same indications of 

 the destruction of pre-existing oolitic limestones as those that we 

 have seen in the overlying strata. Thus not only do we find 

 occasional fragments of oolitic limestone in which several broken 

 oolite-grains are still united by the calcite-matrix, but we even 

 find worn oolite-grains serving as nuclei to new oolite-grains ' 

 (PI. XXXIII, fig. 2). 



Another curious appearance seen in these oolitic rocks under 

 the microscope is the indentation of the margins of oolite-grains, 

 usually by angular sand-grains, but sometimes by other oolite- 

 grains or by shell-fragments (PI. XXXIII, fig. 3). It is not easy 

 to frame an explanation of such a structure. The only other rock 

 in which I have detected the same appearance is the Chipping- 

 Xorton Limestone (Bed 22 of Mr. Walford's succession) of Sharp's 

 Hill. That limestone has much more abundant quartz-grains, also 

 its oolite-grains are rather smaller and have sand-grains much more 

 frequently for their nuclei ; but these are differences of degree, 

 rather than of kind. The general appearance of the two rocks 

 is similar, and worn fragments of oolitic limestone occur in both. 



(vi) Lias: Domerian 2 and Charmouthian. [A. IE. D.] 



The change from the variable beds already described to the 

 markedly-uniform Liassic shales was very striking. The writer of 

 this section fortunately saw the greater part of the uppermost 

 100 feet of Lias cores soon after they were brought up, at the end of 

 October 1911 : for, being unprotected from the Aveather, they were 

 soon reduced to mud. The finding of a capricorn ammonite at 



1 [It was suggested by Dr. Matley during the discussion that these derived 

 fragments of oolitic limestone might be of practically contemporaneous origin, 

 being broken-up as soon as formed. This may be so in the last-mentioned 

 case (worn oolite-grains as nuclei to new grains), but I do not think that 

 the explanation can apply to the majority of eases. — A. M. D.] 



2 As it is desirable, on several grounds, to be able to distinguish between 

 the Middle Lias, in the restricted sense of the Geological Survey, and the 

 underlying clays which are also included in the Middle Lias by many authors, 

 I follow Mr. Buckman in restricting the name ' Charaiouthian ' to the latter 

 and adopting for the former Dr. G-. Bonarelli's term 'Domerian' (Rendiconti 

 R. 1st. Lombard, ser. 2, vol. xxviii, 1895, pp. 326, 415). According to 

 Dr. A. Bettoni, the term should properly be ' Domarian,' being derived from 

 Monte Domaro, called Monte Domero by Bonarelli (Mem. Soc. Paleont. 

 •Suisse, vol. xxvii, 1900, No. 3, p. 3, footnote). 



