Vol. 57.] tHtSlCAt DErBLOPMEJfT OF ANGtJlLtA, EtC. 529 



varieties of Orbicella acropora^ Linn., a recent type. Several 

 species of shells in the form of casts are common. Mr. Cleve 

 identified Tellina fausta, Gold., Cerithium litteratum^ Born, C. can- 

 datum^ Sow., Fissurella Listeria d'Orb., and a Bulla—sll except 

 the last being living species, while the Bulla resembles B. granosa, 

 Sow., a form occurring in Miocene beds of Santo Domingo ; so that 

 Mr. Cleve provisionally regarded the formation as late Miocene 

 (which does not occur in the West Indies) or Pliocene. From 

 the presence of recent corals, which are not found in the older 

 Tertiary of Antigua, it seems that the deposit is no older than the 

 close of the Pliocene, the same as the upper beds of Anguilla, 

 Tintamarre, and the Usine Beds of Guadeloupe, yet antecedent to 

 the epoch of stupendous erosion which left Sombrero a lonely 

 sentinel, far out in the ocean, upon the edge of the now sunken 

 Aatillean ridge. 



V. The Newer Formations. 



A mantle of brecciated fragments of the Point-Blanche siliceous 

 limestones covers a portion of the hillsides of south-eastern 

 St. Martin. But where the Point-Blanche limestones have been 

 removed by denudation, the mechanical deposit rests upon the 

 surface of the decayed volcanic rocks. It is newer than the old 

 White Limestones, which have been entirely removed from this 

 locality ; and as it has suffered such extensive denudation, I am 

 inclined to correlate it with certain mantles in Antigua and 

 Guadeloupe, which are provisionally regarded as belonging to the 

 close of the Pliocene Period, and equivalent to the Lafayette 

 formation of the American continent, in time about that of the 

 deposition of the upper marls of Anguilla, Sombrero, etc., which 

 were accumulated at a distance from the source of supply of such 

 mechanical debris. 



Another entirely distinct and more recent deposit is seen on the 

 hill above Pelican Point, in the remains of a mantle of rounded 

 waterworn gravel composed of igneous rocks, so recently water- 

 worn and elevated that the surfaces of the pebbles are not yet 

 decayed. The pebbles are mixed with the thin layers of rock- 

 debris which are creeping down the hillside : they occur up to a 

 height of 200 feet. On the north side of the divide, between 

 Philipsburg and Oyster Pond, is almost a boulder-pavement at 

 190 feet above the sea. This was probably a residual or other 

 accumulation left by the waves of the sea at the same time as the 

 gravels seen on the hills. 



Along the shore of Crocus Bay in Anguilla is a reddish sandy 

 deposit overlying the limestones.^ It is regarded as the equiva- 

 lent of the waterworn St. Martin gravel. These loams and gravels 

 are represented in the same geological position in the other islands,'^ 



1 At another point, overlying the upper marl is a mechanical deposit forming 

 a thin mantle which may have been washed from the higher land, 



^ The Cassada-Garden Gravels of Antigua, the Lower Petit-Bourg loams 

 and gravels of Guadeloupe, others of St. Kitts, etc. 



