372 
TEHTIART 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 tliat 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) ; 
at the ridge of tlie Cerro de Meapire, near Cariaco ; at Cabo’ 
Blanco, on the west of La Guayra, and on the shore of Porto 
Cabello ; they are consequently found at the foot of the 
two slopes of the northern cluiin 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 re(!ent beds) appears to me to constitute but one 
formation, which is found at the Cerro de la Popa, near Car- 
thagena, and in the islajids of Guadaloupe and Martinico. 
Such is the geological distribution of strata in the moun- 
tainous part of Venezuela, in the group of the Parinie, and 
in the littoral Cordillera. IVe 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 clayejr cement, extremely tenacious, olive-brown, some- 
rimes ot a vivid red : 2nd, a compact limestone, (between 
Tisnao and Calabozo) which, by ita 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 apjieared 
to me to succeed e^h 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 iinmo- 
