440 SCIENCE PROGRESS. 



should take upon itself the production of a map more in 

 accordance with modern needs. 



By far the greater part of Portugal is occupied by ancient 

 rocks of Archaean and Palaeozoic age, and by eruptive 

 masses which probably belong to various periods. All the 

 higher mountains are formed of such rocks ; and it is only 

 in the plain of the Tagus and along the coasts that any later 

 beds are to be found. The most extensive area of Mesozoic 

 rocks forms a broken triangle with its base parallel to the 

 Tagus between Lisbon and Torres Novas, and its apex at 

 Oporto. Mesozoic rocks also occupy a narrow strip of 

 country along the southern shores of Portugal in the 

 province of Algarve. They are found too in the Serra da 

 Arrabida, which forms the prominent cape south of Lisbon ; 

 and at Sao Thiago de Cacem and Cabo de Sines farther 

 south. The largest area of Tertiary deposits is that which 

 forms the plain watered by the Tagus and its tributaries. 



" Azoic " Rocks. — The so called Azoic rocks, in which 

 no fossils have hitherto been discovered and which are pre- 

 sumed to be older than the Cambrian, are best developed 

 east of the Tertiary basin of the Tagus in the province of 

 Alemtejo. But it cannot be said that their age has been 

 determined with certainty, and the supposed absence of 

 of fossils may be due to imperfect examination. 



Lower Palceozoic. — In spite of the extensive area occu- 

 pied by schists and other rocks of supposed Palaeozoic age 

 undoubted Cambrian fossils have been found at only a 

 single locality in Portugal. So long ago as 1876, between 

 the "Azoic" rocks of Alemtejo and the Lower Carboniferous 

 of the borders of Algarve, Delgado recognised a series of 

 beds which he believed to be distinct from both ; and in 

 this series, near the mines of San Domingos, were found 

 Nereites and other forms which are usually believed to be 

 tracks of animals. They are quite insufficient to determine 

 the age of the beds, and it was chiefly from a lithological 

 resemblance to certain rocks in the North of Portugal that 

 Delgado referred them to the Cambrian (15). 



More recently (21), however, trilobites have been dis- 

 covered near Villa Boim, some 10 km. west of Elvas ; and 



