1867.] DUNCAN WEST-INDIAN CORALS. 11 



There are very few solid data upon which the age of the Trinidad 

 deposits can rest; but Mr. Etheridge long since* distinguished the 

 Midtertiary facies of some shells; and Mr. Guj^py lately f has satis- 

 factorily correlated the deposit whence they came with the Miocene 

 deposits of the northerly islands. The Miocene beds:|:> ^^ which the 

 fossils occur, rest conformably upon highly inclined indurated clays, 

 coarse-grained sandstones, and compact limestones of Cretaceous age. 

 This Cretaceous series is said to be of Neocomian age, and is there- 

 fore not to be referred to the same date as the Jamaican Cre- 

 taceous series. Wall and Sawkins named the Trinidad Cretaceous 

 series the " Older Parian : " it stretches very nearly midway across the 

 island from west to east ; and the Tertiary deposits flank it to the 

 north, south, and east. There is an outlier of the Older Parian in the 

 south of the island ; and in a synclinal trough a part of the Naparima 

 series (the fossiliferous Miocene) rests immediately upon the Creta- 

 ceous rock. But, although in contact in the south, there is a band 

 of clays, shales, and yellowish limestones (the J^ariva series) which 

 separates the two series in the middle of the island. 



The fossiliferous deposit at St. Croix, near Savanna Grande, whence 

 the fossil Corals were derived, is in the portion of the Naparima 

 series which is separated from the Cretaceous strata by the Nariva 

 series. On the northern side of the Older Parian rocks this Nariva 

 series is not repeated ; but a limestone, massive or granular, and 

 often crystalline in its character, succeeds at once. Like the Wapa- 

 rima series, it is fossiliferous ; but there are no satisfactory data, only 

 extreme probability, to prove that this Tamana series is to be core- 

 lated with the Nariva or the Naparima deposits. There is a great 

 mass of deposits resting on these limestones of the Tamana series, 

 and occasionally on the Older Parian rocks, and stretching away to 

 the north ; they are often rendered highly carbonaceous by lignites, 

 and are more recent than the Tamana limestones. 



Corresponding with these carbonaceous deposits of the north, there 

 is a great arenaceous series in the south which rests upon the Napa- 

 rima deposits. The porcellanites, lignites, and natural asphalts 

 of this southern representative of the carbonaceous northern series 

 are the best-known peculiarities of Trinitatian geology. 



The Miocene of Trinidad appears thus under different mineralo- 

 gical conditions on the north and south of the Cretaceous series. A 

 limestone and a lignitiferous series exist to the north ; and a yellow 

 limestone, clays and shales, fossiliferous marls, and an arenaceous and 

 lignitiferous series are found to the south of the Cretaceous rocks. 

 There is apparently no trace of a chalk of the Hippurite age, nor is 

 there anything like the Eocene shales of Jamaica. 



The geological structure of the island is moreover complicated by 

 the range of hills which form the north coast, and whose detritus 

 covers up the northern extremity of the lignitiferous series. This 

 range is, probably, geologically the same as the littoral chain of 



* In " Eeport of Greology of Trinidad," p. 164. 



t J. L. Guppy, Quart. Journ. Geol. Soc. vol. xxii. p. 281 et seq. 



j Wall and Sawkins, op. cit. note 5. 



