686 ME. E. J. LECHMEEE GTJPPY ON THE GEOLOGY [Nov. I9H, 



by Dr. Spencer the Antigua Formation) an antiquity not less than 

 Eocene (for it is probably of the same date as the Orbitoides Bed 

 of Trinidad), I do not assert that all the formations correlated with 

 it are as old. We have sufficient reason for assuming the strata 

 containing Echinolampas ovum-serpentis and Terebratula carneoides 

 in St. Barts to be of that age. It is denied that any Miocene 

 deposits exist in St. Barts ; but the strata of Anguilla containing 

 Echinolampas semiorbis and E. lycopersicus are reasonably considered 

 to be Miocene. 1 Nevertheless, it is probable that Miocene as well 

 as Eocene strata are developed along the course of the Antillean 

 dislocation, and moreover that the formations found along the 

 Lavega Plain in Haiti contain Eocene as well as Miocene strata. 

 The same has been shown by Mr. G. P. Wall to be the case with the 

 Cumana or Cariaco depression in Venezuela, 2 but we still require 

 more evidence on this point from carefully-collected fossils. Cast3 

 of fossils are common in many of these formations, and they simulate 

 equally early Mesozoic and late Tertiary or even recent shells : the 

 inferences drawn from them are therefore misleading, as I can state 

 from personal experience, and as may be seen by reference to many 

 geological papers where Eocene and Miocene fossils in the shape of 

 casts are identified with living species. 



To go into the question of the bearing of the fossil corals of 

 Antigua upon the age of the formations of that island would lead 

 me into an enquiry too complicated for the present occasion. So far 

 as 1 can make out from a perusal of P. Martin Duncan's papers 

 and of Purves's and Gregory's observations thereon, the evidence is 

 uncertain; but doubtless further light will be thrown upon the 

 question by renewed investigation. 



We must now consider the middle region of Antigua, that 

 designated the 'Central Plain'; this name can hardly be said to 

 be appropriate, as the ' Plain ' is not only uneven generally, but 

 several hills rise in a more or less interrupted and irregular range 

 along the middle part of it. The formations of which the ' Central 

 Plain ' is composed are fully described by Purves, who represents 

 them as a series of beds of tuff among which are intercalated 

 deposits of chert and limestone containing terrestrial and fresh- 

 water shells and silicified wood and corals. There is a marine 

 chert, as well as a freshwater chert ; but for details I must refer 

 the reader to Purves's paper. The important conclusion arrived 

 at by him is contained in these words : — 



' La region volcanique qui s'etend depuis les bords rneridionaux du Lac Taupo 



jusqu'au dela de la contree lacustre autour de Tarawera est certainement 



celle qui presente actuellement les conditions les plus analogues a celles dans 

 lesquelles s'est forme le chert d'Antigoa. Cette region repose sur un fond de 

 tuf trachytique et de conglomere, a la surface desquels sont dissemines 

 de noinbreux lacs, marais et lagunes au milieu et sur les bords desquels 

 jaillissent des milliers de sources bouillantes, forteinent chargees de silice 



1 The Miocene age of the Auguilla formation is confirmed by the evidence 

 which the fossil mollusca supply. See Q. J. Gr. S. vol. xxii (1866) p. 574. 



2 See Trans. Canad. Inst. vol. viii (1908-1909) p. 378. 



