228 ME. JUKES-BROWNE AND PROF. HARRISON 



After this explicit statement it seems strange that he should still 

 venture to rely upon the corals alone for determining the age of the 

 West-Indian faunas. He points, however, to the occurrence of 

 some of the corals in other islands, and in formations which have 

 on other grounds been regarded as Miocene. It must, on the other 

 hand, he remembered that our knowledge of the geology of these 

 islands is still very incomplete, and that though there is a sequence 

 of Tertiary deposits both in Trinidad and Jamaica, the relations of 

 the several rock-groups to one another are by no means certain, 

 Erom facts which have come to our own knowledge we are strongly 

 inclined to believe that the true stratigraphical sequence of the 

 Tertiaries in both these islands has yet to be made out. 



Again, on p. 454 (op. cit.) he admits that in Antigua itself the 

 determination of the exact age of the trap, the conglomerate, the 

 chert, and the marl is open to doubt, but says " that these three 

 last strata should be of the same age as the coral-reefs in the 

 surrounding sea is impossible, inasmuch as the silicified corals have 

 a greater resemblance to European fossil forms, and to Pacific and 

 East-Indian recent forms, than to those of the present Caribbean Sea." 

 This argument can hardly be regarded as logical, for the silicified 

 corals occur in the chert, not in the marl, and the chert and the 

 marl may well be of different ages (see infra, p. 231), as indeed we 

 believe they are ; in fact his own lists show that out of 23 species 

 found in the two formations only one is common to both. This 

 species he identifies with Alveopora dcedalea, which occurs also in 

 the Pliocene " "White Limestone " of Jamaica, and still lives in the 

 Pacific Ocean. There is, therefore, absolutely no evidence for the 

 Miocene age of the Antiguan "marl," though according to Prof. 

 Duncan its coral fauna has certain affinities with that now existing 

 in the Pacific. 



He observes that " the absence of simple corals from the collec- 

 tion from Antigua is somewhat remarkable, especially when their 

 prevalence in San Domingo and Jamaica is considered." In this 

 the Antiguan deposits agree with those of Barbados, and the fact is 

 a proof that we are dealing with raised reefs only. " Equally re- 

 markable is the presence of no less than nine species of Astrcea 

 [seven in the marl], some of them second to none in size and 

 development " (op. cit, p. 445). Prof. Duncan thinks that the large 

 blocks of these Astrcea, together with species of Alveopora and a 

 large Bhodorcea^ indicate a reef with Pacific rather than West-Indian 

 peculiarities. In the light of more recent information, however, 

 it is doubtful whether the Pacific affinities of the fossil fauna are 

 so strong as Prof. Duncan at that time supposed. 



With regard to Barbados, the sole evidence on which a Miocene 

 date is claimed for the coral-rock is the occurrence of a species of 

 Aatrcea to which the name harhadensia was then given, and which 

 is described as being more closely allied to the recent A. annularis 

 of the Pacific than to the A. stellulata of the West Indies. A cast 

 of the same species was obtained from the " marl" of Antigua, but 

 it is obvious, from the preceding remarks, that this in no way 



