180 Mr. De la Beche on the Geology of Jamaica. 



cerithia ; of the latter g-enus, besides a smaller species, I met with the gigantic 

 one figured in Plate XXI. and which is also found in a similar situation at 

 Chapelton. Beneath these beds there is a succession of gray and light coloured 

 marls, among which I discovered fibrous gypsum, and thick beds of compact 

 gray blue limestone; the whole resting upon porphyritic conglomerate near 

 Mount Sinai. 



White limestone beds, from one foot to three feet in thickness, have a 

 curved dip to the S.S.E., between Norris and Lloyds upon Vavasers River. 

 Marl, limestone, and slaty beds of the lower part of this formation are seen 

 from the latter place up the valley of the Back River to the ridge that descends 

 from Yallahs Hill*, and separates St. David's from St. Thomas-in-the-East. 

 This connecting ridge, or col as it would be called in Savoy or the French 

 Alps, occurs between the Petersfield and Back rivers, and presents a mixture 

 of white marl, brown sandstone, slate day, and gray marl, with gray and 

 white limestones, in beds nearly vertical, having a direction about N.E. and 

 S.W. Yellowish sandstone should also be added to this list. 



The white limestone formation of St. Thomas-in-the-East comes close up 

 to the submedial country between Spring Garden and Bath ; and, between 

 the former place and Whitehall estate, upon the Plantain Garden River, 

 white limestone associated with red marly sandstone rests upon argillaceous 

 slate. The low hills on the south of Plantain Garden River between White- 

 hall and Sunning Hill are composed of white sandstone and marl mixed with 

 reddish sandstone. Beds of gravel and coarse sandstone are found near 

 Golden Valley, the relations of which to the rocks of the surrounding country 

 I did not clearly ascertain, but they seem to occur beneath the white limestone 

 formation. 



The low hills extending to the sea on the south of Bath are composed of 

 the white chalky marl portion of this formation, and might easily be mistaken 

 for some varieties of chalk. These hills, which reach to the Great Morass 

 near Morant Point, are separated from the white limestone on the north of 

 Plantain Garden River by the diluvial and alluvial plain (rich in sugar estates) 

 which extends from the mouth of the river to beyond Bath, and most probably 

 conceals the junction of the limestone on the south with that on the north. 



The white limestone that forms the coast from the north of Wheelersfield, 

 Hordleys, Amity Hall, and Holland estates round the North-east Point to 

 Port Antonio, presents an association of compact white limestone and white 

 marl, mixed occasionally with some red. At Manchioneal Harbour the white 



* This mountain is stated to be 2706 feet above the sea in Robertson's Map. 



