92 Reports and Proceedings — Geological Society of London. 



niici'oscopic dimensions to 1 inch in diameter. The lapilli are glassy 

 or palagonitio ; but felspar-microlites are rare, and the rock of which 

 they are made has no counterpart among the lavas of the county. 

 The ejected blocks in the ash vaiy from several inches up to 1 foot 

 in diameter, and are similar to the blocks in the vent at Kniveton. 

 Tlie small lapilli scattered through the liuiestones are generally con- 

 verted into calcite or dolomite with oxide of iron. The paper was 

 illustrated by microscopic slides, and horizontal and vertical sections 

 of the cuttings and quarries described ; also by hand-specimens, 

 photographs, and lantern-slides. 



2. "The Oceanic Deposits of Trinidad." By Prof. J. B. Harrison, 

 M.A., F.G.S., and A. J. Jukes-Browne, Esq., B.A., F.G.S. 



" The object of this communication is to present some observations 

 on the succession and geological relations of the beds which have 

 long been known in Trinidad as the Naparima Marls. This name 

 was given by Messrs. Wall & Sawkins in 1860, on account of their 

 occupying a large part of the Naparima district east and south-east 

 of San Fernando. The beds so named formed one of the five series 

 wliich were described by these authors under the head of the Newer 

 Parian Group." In his histoi'ical introduction Mr. Jukes-Browne 

 deals with the writings of Mr. Guppy and Professor Harrison, and 

 shows that three definite issues are thus raised : — (1) Are the Nariva 

 Beds above or below the Naparima Marls? (2) Do the Glohigeriua- 

 marls occur in the Naparima district, and, if so, are the}' connected 

 with the Eadiolarian marls or are the}' part of a separate formation? 

 (3) What is the relation between the San Fernando Beds and the other 

 groups ? Mr. Guppy and Professor Harrison agree in answering 

 the first pai't of the second question in the affirmative, and in stating 

 that the two marls are closely connected together. 



In the second part of the paper Professor Harrison tabulates the 

 following succession in the Naparima district : — 



3. Radiolarian beds resembling those of Barbados. 1 



2. Grey Globifferina-maxls, the same as those of the I Oceanic Series. 



coast- section. J 



1. Eed and blue clays. Nariva Beds. 



Although junctions of the Nariva Beds and the Oceanic Series are 

 not seen, at Ste. Madeleine Usine the cla^'S of the former series 

 occur 30 feet lower than the Globigei-iua-iiiarls, and there appears 

 to be no transition between the two series. On the other hand, the 

 transition between (2) and (3) appears to be complete. A com- 

 parison with the corresponding beds at Barbados now becomes 

 possible, and this shows that the Gl obiyerina-vaa.rls occupy the place 

 of the basal clialks of Barbados, but are much thicker, while the 

 radiolarian rocks are thinner, and the interbedded volcanic ashes 

 so irequent in Barbados are wanting in Trinidad. Chemical and 

 microscopic analyses of the Glohigerina and radiolarian beds are 

 given, and, compared with similar analyses of the Barbadian 

 deposits, they show that more quartz and argillaceous matter occur 

 iu Trinidad. The radiolarian marls contain iridescent scales due to 



