the Neighbourhood of Lisbon. 121 



In the whole of the district round Cintra, the formation consists of thick heds of 

 coarse grey limestone, alternating with thinner beds of shale or marl : at the bottom 

 of the formation the limestone beds are thinner, of a darker colour, a more earthy- 

 structure, and a slaty fracture. 



The hills along the coast, from Cezimbra to Cape Espichel, consist of the same 

 formation. Beds of coarse grey hmestone alternate with layers of shale, marl, and 

 sandy clay, but the argillaceous beds are less important there than near Cintra. The 

 dip of the strata is nearly north, varying from 45° to 70°; but at Cezimbra Castle, 

 an igneous rock has caused great disturbance in them. The lowest beds are not 

 exposed in this district, nor is the formation upon which they rest. 



The lofty ridge of the Serra de Arrabida may possibly belong to the same for- 

 mation, but I have no conclusive evidence upon that point. It consists of a com- 

 pact, light grey limestone, with partings of marl only between its lower beds, which 

 have a similar earthy character and slaty fracture with those near Cintra. It agrees 

 very nearly in strike and dip with the limestone ridge of Cape Espichel, from which 

 it is separated by a fault at Cezimbra; but the absence of the alternating shales and 

 marls, so marked near Cintra and Cape Espichel, renders the identity of the two 

 deposits doubtful, and, unfortunately, I met with no fossils in the limestone of the 

 Serra de Arrabida. 



The strike of the beds in the Serra de Arrabida is nearly east and west, and their 

 prevailing dip is north at a high angle ; but at the western end of the Serra the dip 

 varies to N.W. and N.E., and on the northern side of the Serra de Vizo, it is 45° 

 S. At these last-mentioned spots, the limestone rests unconformably upon the 

 older red conglomerate. 



Near St. Ubes are two detached points of limestone which appear to belong to 

 the rock of the Serra de Arrabida : the one forms a conical peak on the east side 

 of the road from Palmella to St. Ubes, its beds dip S.E. about 80° (Sect. 9.) ; the 

 other rests upon the older red conglomerate at the southern side of the Serra de 

 San Luiz, and dips 45° S, (Sect. 13.) ; both these masses approach to conformity 

 with the limestone of the north side of the Serra de Vizo. 



Organic Remains. — The following shells were found in this formation : — 



Trigonia scabra, Deshayes, Coquilles Caracteristiques des Formations, 1. 13, f . 4 and 5, a species consi- 

 dered characteristic of the green sand in France, and common in the green sand at Blackdown, Devonshire. 



Nerinea Defrancii, Deshayes, Expedition de Moree, i. 26, f. I and 2 (iV. svprajurensis of Voltz), found 

 also in the coral-rag at St. Mihiel, in the Neocomian beds at Neuchatel, and in the upper green sand of 

 the Morea. 



Nerinea , another species undescribed. 



Ostrcea colubrina, Goldfuss, t. 74, f. 5, found in the coral-rag of Wurtemberg. 



Exogyra plicata, Goldfuss, t. 87, f. 5, a species found in the chalk in France and Belgium, and abun- 

 dant in the Hippurite limestone near Lisbon (ante p. 116). 

 VOL. VI. SECOND SERIES. R 



