M. B. Lewy's Expedition to New Granada. 131 



situate, at a height of 2661 metres* Santa Fe de Bogota. 

 Mr Lewy explored the mountainous regions to the north 

 of that city, in the direction of Velez, de Tunja, de Muzo, 

 &c. In ascending the course of the river Magdalena, he exa- 

 mined the alluvium of that river. Among the blocks rolled 

 by the water of this river were masses of mica-slate, sienite, 

 diorite, porphyry, sandstone, and varieties of black limestone- 

 On the banks of the Magdalena, in other points of the valley, 

 he observed a recent conglomerate, consolidated by a ferru- 

 ginous base. 



The table-land of Bogota and the mountains which vary 

 its surface are formed of a very thick calcareous deposit, 

 composed of numerous beds of red and white sandstone and 

 schist, and of carburetted black limestones. These rocks had 

 already attracted the attention of several observers, as Hum- 

 boldt and Boussingault. More lately the Baron Gross ob- 

 served and described with care the white sandstones which, 

 in great masses, form the picturesque and singular escarp- 

 ments of the Pont di Pandi, and also those from which is 

 precipitated the celebrated waterfall of Tequendama. 



The sandstones, whether red or white, contain no fossils, 

 but such were found in several points in the beds of black 

 limestone. 



M. Lewy visited the fossiliferous localities where MM. 

 Boussingault and Degenpart had already made collections 

 which enjoy a just celebrity, and of which the species have 

 been described by MM. de Buch and d'Orbigny. He has 

 added many new species to those collected by his predeces- 

 sors. We may mention Crioceras Lewy anus, Val. de Velez, 

 one of the most beautiful which exists in any collection in 

 Paris, and different species of Ammonites, d'Exogyres, of 

 Trigonia, of Inocerama, &c. 



Viewed in a general way, these fossils seem to confirm the 

 conclusions which Buch and d'Orbigny have arrived at, by 

 the study of the collections of MM. Boussingault and Degen- 

 part, viz., that the great sedimentary table-land of Bogota 

 corresponds to the lower cretaceous deposits of Europe, and 

 particularly to that stage of those formations known under 

 the name of Terrain Neocomien. 



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