64 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



and contains much rounded shingle ; but it has no great extent, as 

 the Oohte series of Calvados rests immediately on rocks of the Silu- 

 rian age. No beds referable to either of these formations are to be 

 found beneath the Oolites, from the Boulonnais as far as the valley 

 between the ranges of the Ardennes and the Hundsriick, near Lux- 

 embourg. The Triassic group passes E. of the old land-surface, 

 along the valley of the Weser, where it rests on the coal-measures 

 near Osnabruck. Heligoland also presents characteristic Bunter- 

 Sandstein and Muschelkalk. There is therefore a large extent of 

 surface, ranging E. and W., over which beds of this age are entirely 

 wanting. Researches which have been made beneath the Chalk show 

 that it is wanting along a line of twenty-five miles to the N.E. of 

 Marquise ; and, as it is absent over the Mendip ridge, we may infer 

 that it stands in like relation to any line which may connect these two 

 points. 



§ 2. Oolitic Series. 



No beds of this age ever appear to have been deposited over an 

 area more than equalling the whole of England in extent, ranging 

 through eighteen degrees of longitude, from the German Ocean east- 

 wards, and with a breadth of four degrees of latitude, if not more ; for 

 it is difficult to determine to what extent the German Ocean area was 

 one of dry land at this period. 



The Oolites of Yorkshire and Lincolnshire were dependent on a 

 land which lay to the east ; and this consideration is of importance, 

 as far as antecedent geographical arrangements affect our present 

 inquiry. 



From Tournay to Hirson, no beds of Oolitic age occur between 

 the Palaeozoic and Cretaceous formations. At Hirson, deposits are 

 met with which represent imperfectly any of our subdivisions of this 

 series, but which may be taken as the equivalents of the sub-medial 

 portion — from the Lias to the Cornbrash inclusive ; the whole being 

 much reduced in thickness, and overlaid unconformably by the Cre- 

 taceous group. 



In the Boulonnais, which, though more than 100 miles distant, is 

 the nearest point at which the Oolite series again occurs, the lowest 

 beds are seen, as at Leulinghen, resting on Carboniferous Limestone. 

 The Oolitic group, as here exhibited, extends from the Coral rag or 

 Great Oolite up to the Portland beds ; for here again, as at Hirson, 

 the grouping of the fossils is not so definite as in our S.W. counties. 

 About Marquise, the oolitic beds set on with all the usual characters 

 of somewhat shallow-water conditions, and on a surface much worked 

 over by perforating animals : in all respects the conditions correspond 

 with those of the Department of the Aisne*, and showing that the 

 Oolitic series was limited and influenced at both places by a pre- 

 existing ridge of old strata. Beds of Oolitic age were wanting beneath 

 the Cretaceous strata in the trial-shafts at Tilloy and Monchy-les- 



* D'Archiac, Mem. de la Soc. Geol. de France, torn. v. 



