i GGLOMEItATED LTMESTONES. 
"39S 
iageous circumstances tlian I was m)'self, may direct thoir 
researches. 
XII. Agglomehate Limestone oe tue Baeicon, of 
THE Castle of Cumaha, a:sd of the vicixity of 
P oETO Cabello. — This is a very complex formation, pre- 
senting that mixture and that periodical return of compact 
limestone, quartzose sandstone, and conglomerates (lime- 
stone breccia) which in every zone peculiarly characterises 
the tertiary strata. It forms the mountain of the castle ot 
San Antonio near the town of Cumana, the south-west 
extremity of the peninsula of Araya, the Cerro Me.apire, 
south of Caraco, and the vicinity of Porto Cahello. It con- 
tains (1) a compact limestone, generally of a whitish grey, or 
yellowish white (Cerro del Barigon), some very thin layers ol 
which are entirely destitute of petrifactions, while others are 
filled with cardites, ostracites, pcctens, and vestiges of litho- 
phyte polypi : (2) a breccia in which an innumerable number 
of pelagic shells arc found mixed with grains of quartz 
agglutinated by a cement of carbonate of lime : (8) a cal- 
careous sandstone with X'eiy fine rounded grains of quartz 
(Punta Arenas, west of the village ot hlaniqnarez), and con- 
taining masses of brown iron ore; (I) banks of marl and 
slaty clay, containing no spangles of mica, but enclosing 
selenite and lamellar gypsum. These banks of clay appeared 
to me constantly to term the lower strata. There also 
belongs to this tertiary stratum, the limestone tufa (fresh- 
water formation) of the valleys of Aragua near Vittoria, and 
the fragmentary rock of Cabo Blanco, westward of the port 
of La Guavra. I must not designate the latter bj' the name 
of nagelfluhe, because that term indicates rounded frag- 
ments, while the fragments ot Cabo Blanco are generally 
angular, and composed of gneis.s, hyaline quartz, and chlo- 
ritic slate, joined by a limestone cement. This cement 
contains magnetic sand,* madrepores, and vestiges of bivalve 
sea shells. The different fragments of tertiary strata which 
1 found in the littoral Cordillera of Venezuela, on the two 
slopes of the northern chain, seem to be superposed near 
Cumana (between Bordones and Piuita Delgada) ; in tha 
* This magnetic sand no doubt owes ils origin to chloiitons slate, 
which, in these latitudes, forms the bed of the sea. 
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