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ON THE GEOLOGY OF BARBADOS. 217 



the slide from tlie Lightfoot's sample, but no foraminifera in any of 

 them. In the Plumtree Gully sample (80 feet) there are many 

 coccoliths and stellate crystalloids like those described on p. 178. 

 Around some of the latter calcite has crystallized in such a manner 

 as to obliterate the original form. Many are quite free from this 

 peculiarity, but it is quite easy to trace in a number of examples 

 the gradual growth of calcite until an irregularly-shaped minute 

 calcite-crystal is produced. On the coccoliths also a deposition of 

 calcite has taken place. 



The specimen from Plumtree Gully at 69 feet appeared to be a 

 concretionary nodule of exceedingly fine, white calcareous earth, 

 exhibiting concentric rings of dark brown colour. That from 

 70 feet is a white marly clay, consistinnj largely of minute calcite- 

 crystals with very fine, probably felspathic material. 



§ 7. I^OTES ON THE existence; oe similae Deposits in other 

 West Indian Islands. 



(a) Trinidad. — Beds of white radiolarian earth occur in the 

 !N^aparima district, near San Fernando, on the western side of 

 Trinidad. Their existence has been known for some time, but 

 little information with respect to their geological position and 

 relations has been forthcoming. 



Messrs. Wall and Sawkins made a geological reconnoissance of 

 Trinidad in 1860, and the results were published in a Geological 

 Eeport with map and sections. They describe the Tertiary strata 

 which occupy a large part of the island under the name of the 

 ' Newer Parian Formation,' and distinguish five groups to which 

 they give special names, lettering them A, B, C, D, E, as if they were 

 successive stages in this formation. It appears, however, from the 

 map and from their general section through the island (plate i.) 

 that the ' Older Parian ' (Cretaceous) Series forms an anticlinal ridge, 

 crossing the island from west to east, and having an area of Tertiary 

 rocks both on the south and on the north side, and further that the 

 first two groups occur only on the north side and the other three 

 groups only on the south side of the central ridge. 



On the section the beds on the north side are underwritten ' first 

 (upper) member of the Tertiaries (Caroni formation)' and ' second 

 member of the Tertiaries {Tamana formation) ; ' while on the south 

 side the Naparima formation is marked as ' corresponding to the 

 second member of the Tertiaries,' and the Moruc/a formation as 

 ' corresponding to the upper member of the Tertiaries.' The 

 Nariva formation is called 'the third member of the Tertiaries,' 

 and it would appear therefore that they regarded it as older than 

 the Tamana Group, but they remark that its relation to the ' Older 

 Parian ' was not ascertained and that it was not recognized on the 

 north side of the anticline. 



From the above statements it is clear that the rock-groups 

 described and named by Messrs. Wall and Sawkins were mainly 

 geographical, and that they were uncertain about their equivalency. 



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