8S8 SANDSTONE OF THE LLAN08. 



V. FELSPATIIIC SANDSTONE OP THE OEINOCO. The 

 gneiss-granite of the Sierra Parime is covered in some few 

 places (between the Encaramada and the strait of Baraguan, 

 and in the island of Guachaco), in its western part, with an 

 olive-brown sandstone, containing grains of quartz and frag- 

 ments of felspar, joined by an extremely compact clayey 

 cement. This cement, where it abounds, has a conchoidal 

 fracture, and passes to jasper. It is crossed by small veins 

 of brown iron-ore, which separate into very thin plates or 

 scales. The presence of felspar seems to indicate that this 

 small formation of sandstone (the sole secondary formation 

 hitherto known in the Sierra Parime), belongs to red sand- 

 stone or coal.* I hesitate to class it with the sandstone of 

 the Llanos, the relative antiquity of which appears to me to 

 be less satisfactorily verified. 



VI. FOKMATION OF THE SANDSTONE OF THE LLANOS OF 



CALAEOZO. I arrange the various formations in the order 

 which I fancied I could discern on the spot. The carbu- 

 retted slate (thonschiefer) of the peninsula of Araya connects 

 the primitive rocks of gneiss-granite and micaslate-gneiss 

 with the transition strata (blue and green slate, diorite, 

 serpentine mixed with amphibole, and granular greenish-grey 

 limestone) of Malpasso, Tucutunemo, and San Juan. On 

 the south, the sandstone of the Llanos rests on this transi- 

 tion strata ; it is destitute of shells, and composed, like the 

 savannahs of Calabozo, of rounded fragments of quartz,f 

 kieselschiefer, and Lydian stone, cemented by a ferruginous 

 olive-brown clay. "We there find fragments of wood, in 

 great part monocotyledonous, and masses of brown iron-ore. 

 Some strata, as in the Mesa de Paja, present grains of very 



* Broken and intact crystals of feldspar are found in the todte liegend* 

 coal-sandstone of Thuringia. I observed in Mexico a very singular agglo- 

 merated felspar formation, superposed upon (perhaps inclosed in) red 

 sandstone, near Guanaxuato. 



+ In Germany, sandstones which belong unquestionably to red sand- 

 stone, contain also (near Weiderstadt, in Thuringia) nodules, and rounded 

 fragments. I shall not cite the pudding-stone subordinate to the red 

 sandstone of the Pyrenees, because the age of that sandstone destitute 

 of coal Tnay be disputed. Layers of very large rounded nodules of 

 quartz are inclosed in the coal sandstone of Thuringia, and in Upper 

 Silesia. 



