372 TEBTIART STRATA. 



centre of the island of Marguerita. This clay appears to lie 

 immediately over the mica-slate, and under the calca- 

 reous breccia of the tertiary strata. I cannot decide whe- 

 ther Araya, which is rich in disseminated muriate of soda, 

 belongs to the sandstone formation of the Impossible, which 

 from its position may be compared to variegated sandstone 

 (red marl). 



There is no doubt that fragments of tertiary strata sur- 

 round the castle and town of Cumana (Castillo de San An- 

 tonio), and they also appear at the south-western extremity 

 of the peninsula of Araya (Cerro de la Vela et del Barigon) j 

 at the ridge of the Cerro deMeapire, near Cariaco; at Cabo 

 Blanco, on the west of La Guayra, and on the shore ot Porto 

 Cabello. ; they are consequently found at the foot of the 

 two slopes of the northern chain of the Cordillera of Vene- 

 zuela. This tertiary stratum is composed of alternate beds of 

 calcareous conglomerate, compact limestone, marl, and clay, 

 containing selenite and lamellar gypsum; The whole system 

 (of very recent beds) appears to me to constitute but one 

 formation, which is found at the Cerro de la Popa, near Car* 

 thagena, and in the islands of Guadaloupe and Martinico. 



Such is the geological distribution of strata in the moun- 

 tainous part of Venezuela, in the group of the Parime, and 

 in the littoral Cordillera. "We have now to characterize the 

 formations of the Llanos (or of the basin of the Lower Ori- 

 noco and the Apure) ; but it is not easy to determine the 

 order of their superposition, because in this region ravines 

 or beds of torrents and deep wells dug by the hands of man 

 are entirely wanting. The formations of the Llanos are, 1st, 

 a sandstone or conglomerate, with rounded fragments of 

 quartz, Lydian stone, and kieselschiefer, united by a ferru- 

 ginous clayey cement, extremely tenacious, olive-brown, some- 

 times of a vivid red : 2nd, a compact limestone, (between 

 Tisnao and Calabozo) which, by its smooth fracture, and 

 lithographic aspect, approaches the Jura limestone: 3rd, 

 alternate strata of marl and lamellar gypsum (Mesa de San 

 Diego, Ortiz, Cachipo). These three formations appeared 

 to me to succeed each other in the order I have just described, 

 the sandstone inclining in a concave position, northward, on 

 the transition-slates of Malpasso, and southward, on the 

 gneiss-granite of Parime. As the gypsum often iinme. 



