183 



MESSRS. J. B. HAREisoN & A. J. jrE:ES-Biiow:sE [Maj 1899, 



entered as argillaceous matter is higher in Barbados. This, how- 

 ever, is probably due to the larger quantity of pumieeous and 

 volcanic dust present in the Barbadian earths. 



Mr. Guppy has described the Globigerina-marls of Naparima as 

 containing from 80 to 90 per cent, of calcareous matter ; ^ but 1 am 

 inclined to view this estimate with some distrust, for he afterwards 

 states that, upon washing, about half the material passes off as fine 

 mud, and that half of the remainder consists of indeterminable and 



Pig. 2. — Comparison of the rock-succession in Trinidad 

 and Barbados. 



Barbados. 



Trinidad. 



Eadiolarian earths. 



Passage-beds 



Globigerina-vaarls .. 



Nariva Series 



1\ I I. Ill' 







Volcanic mudstones. 



Eed clays. 



^O^i^fno:- 



£.'- 



-TC 



/////// 



Upper chalks. 



Calcareo-siliceous 

 beds. 



Pure radiolarian 

 earths. 



Calcareous earths 

 and Chalks. 



Scotland Beds. 



[Scale : 100 feet ^^^ 1 inch.] 



amorphous particles, bits of pumice, iron-pyrites, etc. I question 

 whether any of the Trinidad Olobigerina-ma.ils contain as much as 

 60 per cent, of calcareous matter. 



In describing the radiolarian marls, he mentions that half of 

 the rock is made up of ' small scales and lumps of a pearly grey 

 colour and iridescent surface.' ^ In the specimen examined by me 

 these are present to a certain extent, but do not form more than 



Quart. Journ. Geol. Soc. vol. xlviii (1892) p. 528. 



^ Ibid. loc. cit. 



