152 Geological Society : — 



between it and the mainland, is composed of flagstones, slates, and 

 schists, with quartz-veins and some dark- coloured intercalated lime- 

 stone. These rocks are all apparently unfossiliferous ; the slates 

 often abound with iron, and some of the quartz-veins are slightly 

 auriferous. Stalactitic caves occur in the limestone of the Island of 

 Gaspar Grande, and at Las Cuevas and Arouca. Alluvial beds of 

 clay and gravel are extensive in this district, and are sometimes 

 60 feet thick. At Lateen Bay, in Chicachicare Island, a patch of 

 aluminous clay-slate occurs, with seams of crystalline limestone. 

 The soil of this northern district is fertile on the limestone, and 

 barren on the slates. The slate-rocks appear to be the same as those 

 of Venezuela, which overlie quartz-rock at Upata ; and rounded 

 boulders of quartz-rock occur in the flagstones. 



In the south of the Island of Trinidad, red sandstone abounds, 

 often ferruginous, and associated with clays which are often either 

 bituminous or pyritous, and contain lignite and impressions of dico- 

 tyledonous leaves. In the Erin district the clay-beds have been 

 sometimes indurated and jasperized by heat. They affbrd also small 

 chalybeate and sulphuretted hydrogen springs, and in the blue-clay 

 formation are found hillocks throwing up mud and water, and ponds 

 covered by a film of mineral tar. The mud-volcanoes throw up saline 

 water and greyish mud, in a cold state, with iron-pyrites and water- 

 worn pebbles of blue limestone like that of the northern part of the 

 Island, and sometimes of sandstone. They do not appear to be 

 connected with the sea ; and are most active at the close of the 

 rainy season. At Moruga small hills of granular limestone occur, 

 llie succession of deposits in this southern part of Trinidad appears 

 to be — beginning from below — 1. Sandstone, variegated sands, 

 lignitiferous clays (sometimes jasperized), and the Moruga lime- 

 stone ; 2. Blue and brown clays, with bitumen; comprising the 

 pitch-lakes, salt and alum springs, &c. ; 3. Modern marine sand 

 foimation, from 50 to 100 feet thick ; and alluvial deposits, seldom 

 more than 30 feet thick. 



The eastern coast of Trinidad appears to consist of the red sand- 

 stones and bituminous clays as far north as Matura, beyond which 

 the clay- slates set in. 



The western coast of the island, south of Port of Spain, which is 

 built of the slate-rocks and limestone, exhibits only modern alluvial 

 deposits, sometimes calcareous, frequently ferruginous, and resting 

 towards the south on the red sandstone of the southern district. 



5. "On the fossils found in the Chalk-flints and Greensand of 

 Aberdeenshire." By J. W. Salter, Esq., F.G.S., and W. Baily, Esq. 



A notice of the occurrence of chalk-flints and greensand in Aber- 

 deenshire has been published by W. Ferguson, Esq., F.G.S. in the 

 Proceed. Glasgow Phil. Soc. vol. iii. p. 33, and the Phil. Mag. 1850. 

 p. 430, and some of the facts had been previously noticed ; but no 

 lists of the fossils had been given. This communication showed 

 the presence of characteristic Upper Greensand fossils in the low 

 ground at Moreseat : Thetis minor, Area carinata, Pinna tetragona, 

 and Galerites castanea. The Lima elegans of Nilsson is a new fossil 

 for Britain, and is found with the ordinary Inocerami and Echinites 



