REVIEWS. 



235 



of Santandar, an area some 60 miles by 25, and an outline of the geology. 

 Mountain- chains are its dominant physical feature, the southern boundary 

 resting on the Cantabrian chain. The centre and south-west of the pro- 

 vince are occupied, according to the authors, by two groups of rocks ; one, 

 the most massive, and constituting some of the highest peaks of the south- 

 west, is represented chiefly by a limestone remarkably jagged in its out- 

 lines, hard and splintery, generally white externally, where exposed, but 

 greyish internally, and often almost black in its lowest part. At its base 

 this limestone seems to be associated with a hard grey sandstone rock, 

 and both rest unconformable on thick beds of slate-clay. Beds of con- 

 glomerate, formed chiefly of quartz pebbles, with an extremely hard 

 siliceous cement, are associated with the slate-clay. The limestone rocks 

 appear very much upheaved, and the strata are of the nearly vertical, and 

 forming a succession of anticlinals, the general strike of which may be 

 taken as E. a few degrees W. 



The second group of rocks consists of beds of variegated clays alter- 

 nating with soft sandstone beds of slate-clay, thin beds of marly limestone 

 of a dark grey colour alternating with thin layers of black marly clay. 

 The predominating colour of the sandstones is red. The limestone rocks, 

 upon which the beds of clay, sandstone, etc. rest, rise to the south and 

 south-west in the lofty mountains of the Picos de Europa. 



After detailing with full particulars numerous sections, the author 

 attempt to summarize and deduce the stratigraphieal succession and 

 relative ages of the different rocks. To do this, they first take such hori- 

 zons as are naturally sufficiently definite. The nummulitic series offers 

 one which is not only convenient as the newest or uppermost, but is also 

 topographically the first, being near the sea-shore. The nummulitic rocks 

 rest on cretaceous beds, which occupy a narrow band of country near the 

 sea, in the west of the province, and become largely developed towards the 

 east. Those on the north side of the Bay of Santandar have been studied 

 by M. de Yerneuil, who considers the beds lying between the Bay and 

 the lighthouse to belong to the Upper Chalk Marls, and the authors suffi- 

 ciently establish their position as the first horizon below the nummulitic 

 beds. Those beds which form the quay of Santandar strike off towards 

 the west, and are found not only to overlie the dolomite of Pefla Castillo 

 and the immense mass of the same rock lying about the south-w T est of the 

 Bay of Santandar, but may be traced along the coast up to San Pedro, 

 and inland to Eeocin and La Florida. This dolomite is in some places 120 

 metres thick. The beds which underlie contain Calamophyllia StoTcesii, 

 liliynchonella rimosa, Ostrea deltoidea, Photodomya lyrata, Ammonites 

 bifrons, Ammonites serpentinus. Pectens and belemuites are seven, which 

 are undoubtedly jurassic, while in the dolomite itself ammonites similar to 

 those of the underlying beds. The authors therefore put this dolomite at 

 the top of the jurassic series, and make of them a second well-defined 

 horizon. 



About the upper boundary there can be no difficulty, but it is otherwise 

 with the lower limits. Beneath the dolomite are a series of beds of hard 

 shelly argillaceous limestone, with variegated clay-beds passing into red- 

 dish-grey sandstone, beneath which are thick beds of red micaceous sand- 

 stone ; next follow the beds of compact blue or black limestone, containing 

 metalliferous deposits, and forming* the axis of the east and west chain 

 called the Dobra. Beyond Monte Dobra, in the valley of Los Corrales, 

 there is a repetition of the thick beds of red sandstone. In the upper 

 members of this series many jurassic fossils have been found; but, accord- 



