Geology of Antigua. 79 



piila, pecten, cardium, strombus, cerithium, ostrea, trochus, cy- 

 prea, turritella, venus, lucina," &c. These are sometimes found 

 entire, but they generally occur in the form of casts, either calca- 

 reous or silicious. Dr. Nugent 'also mentions several species of 

 land and fluviatile shells, belonging principally to the genus He- 

 lix, which he has observed associated in the same locality with 

 marine genera, as murex, area, nerita, purpura, chama, trochus, 

 &c. The most of these fossils have living exemplars in the sur- 

 rounding seas. From the specimens which came in my way, 

 (for I did not see a complete collection,) I think I should be safe 

 in estimating the proportion of such as high as 70 per cent. 

 If this estimate be taken as an approximation to the truth, the 

 formation must belong to the latest tertiary or newer Pliocene pe- 

 riod of Lyell. No relics of mammalia have yet been discovered 

 in this group, nor indeed in ahy upon the island.* 



As to the age of the clay formation, I have not sufficient data 

 to form an opinion. With the exception of some petrified leaves 

 found near its junction with trap at Drew's Hill, I could not as- 

 certain that any organic remains had been discovered in it. 

 These leaves belong to trees of the dicotyledonous class. Dr. 

 Nicholson thinks he recognizes among them those of the Ficus 

 pertusa, and a species of Melastoma. The mineralogical charac- 

 ter of these rocks certainly does not indicate great age ; still, 

 neither this nor any thing in their relations to other rocks, points 

 out their absolute place in the series of geological formations. 

 We must wait, therefore, for farther light on this point, till their 

 organic contents are better investigated. 



Intimately connected with the clay formation, if not constitu- 

 ting a part of it, is another class of rocks of a most interesting 

 character. I refer to the extensive beds of chert and the silici- 

 ous petrifactions with which this part of the island abounds. 

 Dr. Nugent describes these beds as a distinct deposit, lying above 

 the clay and below the marl. His opinion is probably well found- 

 ed ; but they are so intimately associated with the clay formation, 

 that I prefer to class them with that group. Their comparative 

 extent is not great. They are found principally in the neighbor- 



* Of the age of the corresponding formation in Barbadoes I can speak with 

 greater certainty. Of forty one species of conchifera and mollusca, which I ob- 

 tained during ten days' residence upon the island, there were only three which are 

 not found at present in a living state in the West Indies. 



