Guppy — West Indian Geology. 497 



fore, not so improbable that the submergence of the Atlantic and 

 Pacific continents was, in part, contemporaneous with the upheaval 

 of large areas in Eurojje and America.^ 



It is possible that we have here an explanation of the com- 

 paratively limited development of Tertiary formations in North- 

 America. They are, as we know, chiefly confined to the region about 

 the Mississippi, and to a narrow belt which extends along the Atlantic 

 coast. This small development of Tertiary rocks may be due to 

 the submergence of the area whence the material for the formation 

 of the American continent was formerly derived. A careful study 

 of the physical geology of the whole region under consideration 

 would alone enable us to generalize with safety on this point. 



2. A further search in the Lower Miocene beds of San Fernando, 

 in Trinidad, has been rewarded by the discovery of a shell hitherto 

 only known by a few examples, obtained by Sir Eobert Schomburgk 

 from a rock in Barbados, and which was described by Professor 

 Forbes. It is possible that we may hence derive some clue to the 

 age of the Barbados older Tertiary, which is as yet undetermined. 

 In order to be clearly understood I shall give a veiy brief outline of 

 the geology of Barbados. 



Two formations are exposed in Barbados. They have been named 

 respectively the Coral formation and the Scotland formation. Of 

 these the former appears by its included organic remains to be of 

 the same age as the Newer Pliocene deposits of the West Indies. 

 All the species are still existing. The Scotland formation contains 

 the well-known microscopic organisms described by Ehrenberg, and 

 called by him Polycystina. In an " isolated rock " in this formation 

 Sir Eobert Schomburgk found some fossil moUusca. Of these, 

 three species alone were in a state to admit of description, and they 

 were named by Professor Forbes, who was inclined to regard them 

 as Miocene. From that time (1846) to the present no further 

 examples of these fossils have been discovered. I had the good 

 fortune to find one of them (the Nucula SchomburgTci of Forbes) 

 in a greenish-gray shale among the middle beds of the Lower 

 Miocene series of San Fernando. The Nucula in question is a re- 

 markable species, resembling, especially in the character of its 

 ornamentation, the N. divaricata of the Pacific, and the N. Cobholdice 

 of the English crag. In the San Fernando beds fossils are rare, and 

 difficult of extraction. Several other species accompany the Nucula 

 in the bed of shale ; but, although enough is seen of them to indicate 

 that they probably belong, in most cases, to undescribed and extinct 

 species, they are rarely in a condition for description. 



Our information as to the relation of the " isolated rock " con- 

 taining Nucula SchomburgTci to the Scotland formation is not so 

 precise as might be wished ; but, assuming it to be a detached pin- 

 nacle or boulder belonging to the Lower Miocene it w;ould thus 

 appear that the Scotland formation is newer than the Lower Miocene, 

 and may possibly, considering that it is inferior to the Pliocene, be 



^ Dana, op. cit., pp. 531, 532; and Lyell, Principles, 8tb. ed., p. 121. 



VOL. IV. — KO. XLI. 32 



