12 GEOLOGICAL MEMOIRS. 



SO many deposits of water, whicli, in seeking to escape, flows under- 

 ground throngh tlie most porous beds of the formation. 



These calcareous tuffs may he seen on hoth flanks of the moun- 

 tains of Alcaraz, both on the side of Riopar and at Yillanueva de la 

 Fuente, with this pecuharity, that in the tuff we find numerous re- 

 mains of the same shells which characterize the other tertiary basins, 

 mixed moreover with the remains of plants which do not now grow 

 naturally in those districts, but which are characteristic of the ter- 

 tiary period. 



With regard to the boundaries of this tertiary basin, the author 

 can only state that towards the north it is determmed by the south- 

 ern slope of the mountains of Toledo and its ramifications, and to 

 the south by the northern flank of the Sierra Morena. In other re- 

 spects this lake cannot have been of such extent as those above men- 

 tioned ; and wben we take into consideration the country in the neigh- 

 bourhood of Taldepeiias towards Santa Cruz, we may be assured that 

 it must undoubtedly have contained several islands of greater or less 

 magnitude. 



This interesting paper is followed by another by the same author, 

 describing in detail the different barriers of these tertiary basins, by 

 the gradual or sudden breaking up or wearing away of some of which 

 the different districts have been drained. 



In the fourth volume there is a memoir by the same author, giving 

 a description of the mines of Farena and of the geology of the neigh- 

 bom'hood of Tarragona. In the excavations which have lately taken 

 place near this town an extraordinary quantity of fossils has been 

 found, almost enthely belonging to the species Conus antediluvianus 

 of Brocchi and C. deperditus of Lamarck, from whence the author 

 coQcludes that the beds belong to the eocene or lowest group of the 

 tertiary or supracretaceous period. This marine tertiary formation 

 extends along almost the whole coast of Spain, as well as that of Italy 

 and of the north of Africa. But it is not only along the coast that 

 it is met with ; in some places it extends far into the interior. Near 

 Tarragona it runs up beyond Reus, forming the basis of the rich plain 

 of Tarragona, contributing by the different elements of its composition 

 to the fertility for which that region is so highly celebrated. 



In the same volume (p. 1 9 1) is another memoir, by Don Jose Aldama, 

 giving geological and mining remarks on the province of Huesca, and 

 part of that of Zaragoza, or the territory designated as Upper Ara- 

 gon. As in the former part of these extracts, I confine myself to that 

 portion which describes the tertiaiy deposits of this district. The 

 details are not so full as could be desired, but they are all the author 

 was able to collect. 



Many spots on the left bank of the Ebro are occupied by tertiary 

 freshwater formations ; but the component parts and strata are not 

 the same in all places, owing to the different causes fi'om which they 

 have resulted. One of the so-called tertiary basins or formations ex- 

 tends through the region of Tamarite in the province of Huesca, and 

 is composed of marls, hmestones, sandstones, conglomerates, and gyp- 

 sums of all kinds and colours. On the banks of the Cinca, in the 



