22 



The author offc>rs no opinion as to the tertiary epoch to vvliich 

 the formation may belong, for the shells obtained at Estavan, al- 

 though entire, were too much flattened to allow M. Deshayes to 

 determine the species. As some portions of the freshwater beds, 

 especially those to the eastward, are highly elevated above others, 

 it appears that the country has undergone great geographical 

 changes since this part of Cerdagne was a lake. 



The position of the tertiary basin of Cerdagne was illustrated by 

 two transverse sections across the Pyrenees. The memoir concluded 

 with some remarks on the signs of obliterated lakes which abound 

 in the valleys of the Pyrenees at a great variety of levels. 



The first of the sections alluded to, extended from Pamiers south 

 of Toulouse through the highest part of the Pyrenees to Puycerda in 

 Spain. Beds of a conglomerate (a), are seen on the river Arriege near 

 Verhilles, inclined to the south; and next in a succession are limestone 

 strata much contorted, containing nummulites and other fossils (b) • 

 then a formation of grit, sandstone and coal, (c). In passing from Ver- 

 hilles t\) Foix the groups b and c appear to be more than once re- 

 peated in consequence of the derangement of the strata. In the re- 

 maining part of the section between Ussat and Puycerda, the rocks 

 consist chiefly of granitic and argillaceous schists, covered here and 

 there by limestone in which no fossils were observed. 



The second section extended from La EstcSla in the low country of 

 Catalonia to Ceret in France. Immediately north of La Estela, which 

 stands upon horizontal tertiary strata, the geologist, on ascending the 

 Pyrenees, finds strata of conglomerate having a southerly dip and 

 probably identical with the group a of the first section. This conglo- 

 merate resembles the pudding stone which caps the lofty hill of Mont- 

 serrat in Catalonia. Next to this comes a nummulitic limestone (b), 

 which is seen at Tarrades, and is also inclined to the south ; then a 

 series of shales and sandstones (c); and next to this, proceeding to- 

 wards the north, a formation of red sandstone and red marl (d). This 

 last is well exhibited in the valley of the river Muga not far from 

 San Lorenzo. It recurs on the north of that valley with a southerly 

 dip, and rests on strata of mica schist and gneiss, which dip to the 

 north. A little to the north of this point the secondary and primary 

 rocks come in contact with opposite dips ; the Pyrenees here consist 

 of gneiss, mica schist and clay slate, which continue to near Ceret, 

 where tertiary formations are seen at the base of the Pyrenees. 



The above section passes through Masanet, to which place Maclure 

 supposed that the volcanic rocks of the Olot district extended. The 

 author searched in vain for any of these modern igneous rocks near 

 that place, and convinced himself that the extent of the modern vol- 

 canic region of Catalonia has been greatly exaggerated, and that it 

 does not stretch in a direction from Olot towards Masanet much 

 farther than Castel Follit, or some point between the last-mentioned 

 town and Besalu. 



