466 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 16, 



bling serpentine. The siliceous strata of this region seem to have 

 been especially affected, since they are frequently veined with 

 vitreous quartz and present their joints coated with crystals of that 

 substance, indicating the solution and re -precipitation of silica. The 

 result of this intercalation of foreign elements is to obliterate the 

 distinctive characters of the two formations, and to render it difficult 

 to determine where one commences and the other ceases. The ten or 

 twelve miles over which this uncertainty prevails was twice ex- 

 amined, but without satisfactorily solving many of the difficulties. 

 In PL XXI. Sect. 3, the circumstances are represented as accurately 

 as could be ascertained ; the place of junction is probably at the point 

 marked J, a short distance north of Villa de Cura, — as the position, 

 hitherto inclined, becomes suddenly vertical, which is accompanied 

 by a variation of aspect, slight indeed, but still perceptible on minute 

 inspection. 



The Morros of San Juan, so named from their castellated ap- 

 pearance, are formed of a grey limestone, compact or subcrystalline, 

 of considerable thickness, and, from the almost obliterated vestiges of 

 fossils, evidently a member of the " Older Parian" formation. It is 

 perfectly vertical in position, and, rising suddenly in the centre of 

 the igneo-sedimentary district from the rounded surface of the sub- 

 jacent hills, in rugged, rocky precipices, and traversing the country 

 in a narrow elevated ridge, offers a natural object of considerable 

 interest. 



At the south-eastern extremity of the Island of Margarita, there 

 is a small basin of sandstones and shales, 600 to 800 feet thick, in 

 which no fossils were detected, nor do they present any mineral fea- 

 tures serving for identification with either the preceding or following 

 series, — forming, perhaps, an intermediate term, of which other frag- 

 ments may be discovered on further investigation. The sandstone 

 is sufficiently indurated to have formed a good material for the con- 

 struction of the old Spanish fort at Pampatar. An angle of 35° 

 indicates the limit of the disturbances experienced. 



The "Newer Parian" formation has been more completely studied 

 in Trinidad*, where it consists of a lower (calcareous) and an upper 

 (arenaceous or shaly) series, by no means clearly distinguished one 

 from another, and rarely presenting the entire development in the 

 same locality. The inferior portion is sometimes composed of lime- 

 stone, often with crystalline texture, or of marls containing sub- 

 ordinate calcareous beds, which are succeeded by calcareous sands 

 and shales. The superior section comprises an alternation of loose 

 sands with carbonaceous shales and occasional conglomerates. On 

 the mainland the calcareous series was only noticed at Cumana, and 

 on the peninsula of Araya ; the superior division, on the contrary, 

 occupies an enormous space, as the llanos or grassy plains of Venezuela 

 are entirely formed of conglomerates, sandstones, &c. referable to 

 this group. The former are especially prevalent, and include 

 numerous rolled fragments of the indurated members of the " Older 

 Parian," which forms the northern limit of the llanos, and which, 

 * See Memoir, No. 1, of Greologieal Survey of the West Indies. 



