The Barrettia Beds of Jamaica. 507 



On the slopes and summit of the hill above the yam-jfields just 

 mentioned the ground is strewn with pebbles, which indicate that 

 the Barrettia limestone is overlain by Trappean conglomerate, 

 though I did not find any actual outcrop of it. This conglomerate 

 must form a capping of 30 or 40 feet on the hill-top, and there are 

 indications of one or two bands of unfossiliferous or sparsely 

 fossiliferous light-coloured limestone in it. 



The pebbles in the Trappean conglomerate consist of — 

 Gneiss with pink felspar and dark mica. 

 Pink quartzite. 



Indurated jaspery much contorted clay slates. 

 Lava of andesite aspect. 

 Dioritic rock. 

 The series is very similar to that which one encounters in several 

 conglomerate beds in the Blue Mountain Series in Jamaica. 



The section of the beds at Haughton Hall, therefore, appears as 

 follows : — 



Feet. 

 " Trappean " conglomerate (including limestone bands) 30-40 

 Barrettia limestone ....... 16-20 



White and grey friable nodular marly limestone . . ^ 



Yellowish grey sandstone . . . , . [• 60 



Grey spheeroidally weathering calcareous shale . . j 



Barrettia is very plentiful in the limestone, and rolled down the 

 slopes below it, and it often occurs in clusters of twos or threes joined 

 together for some distance above the apices. In places in the rock 

 they occur lying on their sides and crushed. Barrettia is a large and 

 solid though comparatively stumpy Rudist, and I did not trace any 

 for a greater length than about 3 feet. The greatest diameter of the 

 large specimens is about a foot. The large crateriform Radiolite 

 a. nicholasi Whitfield also occurs, but is much less plentiful than 

 Barrettia. 



To the westwards the bed of Barrettia limestone seems to have a 

 lenticular shape and to thin out towards the hill slope. Both 

 Barrettia and the large Radiolites seem to be restricted in areal 

 distribution, and the bed in places passes into a hard grey limestone, 

 rather like other Cretaceous limestones of the island. Here and there 

 it shows sections of small Radiolites and other fossils, which, however, 

 are almost impossible to recognize specifically owing to the hardness 

 of the rock. There is a noticeable absence at Haughton Hall of 

 several of the species of corals and other fossils that occur plentifully 

 in other Cretaceous sections in the island. 



The association of fossils and the fact that the Barrettia limestone 

 is overlain by a " Trappean " conglomerate very similar to those 

 commonly associated with the Blue Mountain rocks, and is under- 

 lain by a calcareous shale, proves that it belongs to the Cretaceous 

 series, and is not in any way associated with the Tertiary formations 

 of the island. 



