140 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Nov. 21, 



the deposition of the secondary and tertiary formations, and which 

 covers a large tract round Lisbon. 



There are three separate patches of the hippurite limestone ; one 

 of these is on the west side of Lisbon and extends a few miles down 

 the river to Belem ; this mass of limestone has been thrown into a 

 saddle, of which the axis runs down the valley of Alcantara, just 

 outside the city, with a direction of about N. 30° W., on each side of 

 which the beds dip away from the axis at angles of 5° to 10°; the 

 limestone of many of the beds is shattered to a remarkable degree, 

 and intersected by fissures which run in a direction parallel in the 

 main to the line of the valley, but are waved and irregular. Several 

 of these are sometimes seen in the thickness of a foot, while others 

 are two or three feet apart. There are also three lines on which the 

 beds have been unconformably deposited upon those below, and the 

 fissures just mentioned commence above the lowest of these and end 

 at the upper one ; yet notwithstanding their unconformable depo- 

 sition, the same species of shells are found through all the beds. 

 Therefore the disturbing forces must have acted during the depo- 

 sition of the formation. 



The quarries on both sides of this valley furnish an inexhaustible 

 supply of organic remains. 



Another range of hippurite limestone extends from the shore of 

 Cascaes Bay towards the north-east nearly to Loures, and also spreads 

 out along the coast eastward beyond Passo d'Arcos : many of the 

 hills of limestone are covered with detached masses of basalt, which 

 is itself frequently capped by tertiary beds : and between Oeiras and 

 Fort St. Julian the limestone is directly covered by a large patch of 

 the Almada tertiary limestone full of its usual fossils. 



The remaining line of hippurite limestone reaches from Montelavar 

 and Pero Pinheiro to the hills immediately south of Bucellas, in 

 which a good section is exposed in the ravine leading from Tojal 

 towards Bucellas. At Pero Pinheiro the limestone has been largely 

 quarried and organic remains are plentiful. To the south-west of 

 this place a little correction is required in my map published in our 

 * Transactions,' vol. vi. pi. 14 : the limestone instead of stopping at 

 the farm of Quinta Granzea should be continued in a thin zone round 

 the southern edge of the basalt, till it meets the sandstone on the 

 north of Algeirao. 



The hippurite limestone is laid down in the map just referred to 

 between Villa Franca and Trancozo, and again as extending from 

 Villa Franca to the north-west beyond Alenquer : this is an error in 

 each case, into which I was led by the great resemblance in the 

 mineral character of these limestones to that of the hippurite lime- 

 stone, not having then collected many organic remains : subsequent 

 examination has shown that the limestones in question belong to the 

 lower part of the subcretaceous series, under which head they will 

 be described in due course. ; 



It appears therefore that the hippurite limestone is not to be seen 

 to the north of Bucellas ; nor have I seen it in situ anywhere beyond 

 the neighbourhood of Lisbon ; but it is probable that it occurs near 



