Vol. 54.] Olf THE GLOBIGERINA-MAELS, ETC., OF BAEBABOS. 549 



existence of GIohigerina-rasbTl beneath the coral-rock escarpment 

 east of St. Joseph's Church and below Binfield, for that locality 

 is only 1^ mile from Bissex Hill, and would be traversed by a line 

 drawn from that hill to Bowmanston. 



Indications of the former existence of Glohigerina-heds below the 

 coral-rock of the western slopes have also been noticed ; but the 

 absence of any trace of such beds on Mount Hillaby, at Chimborazo, 

 and at Castle Grant is worthy of remark, for these places are on the 

 highest part of the island (1000 to 1100 feet), and are localities 

 where the highest known members of the Oceanic Series occur. 



If the Globige7nna-Ta.SLTls were ever deposited over the whole 

 island, it is clear that they must have been removed from its 

 highest parts before the growth of the earliest coral-reefs. It is 

 more probable, however, that they never were accumulated over 

 the highest levels, and that these levels were exposed to current- 

 erosion while deposition was in progress over the Bissex Hill area. 

 At any rate, the facts may be explained on the supposition that there 

 was a time in the elevation of the region, and before any part of it 

 became an island, when the central part of the uplift came within 

 the influence of a current strong enough to prevent deposition and 

 to cause some erosion of the soft Oceanic Beds which then formed 

 the surface of the rising dome or ridge. Small lumps of these beds 

 became sufficiently indurated on the sea-floor to be eventually 

 rolled down the outer slopes and embedded in the dense accumu- 

 lation of foraminifera which was being formed round its borders. 



The sequence of the beds on Bissex Hill shows that after a time 

 the introduction of such detritus became less frequent, and that a 

 nearly pure Globigerina-jnarl was formed. Later again the eleva- 

 tory movement was renewed, and the depth of the water diminished 

 more and more ; molluscs, echinoderms, and other creatures con- 

 tributed their debris to the deposit, and currents once more rolled 

 along small pebbles and fragments of the older rocks. 



Ultimately the central dome came within the limits of coral- 

 growth, and an island was formed, the size of which was con- 

 tinually increased, partly by successive elevations, partly by the 

 outward growth of the foraminiferal and coral-debris deposits, 

 this process of building-up being indicated both at Bissex Hill and at 

 Bowmanston by the sequence of Am^histegina-Tock, basal reef-rock, 

 and finally rock full of corals. 



[The facts recorded in the foregoing pages show that the Glohi- 

 gerina-TRBxls must be dissociated from the Oceanic Series and united 

 with the Coral-reef Series. 



Dr. Gregory considers that the coral-reefs were not all formed in 

 the late Pleistocene period, but represent a considerable lapse of 

 time. He regards the higher reefs as probably of early Pleistocene, 

 possibly of late Pliocene age.^ Prof. Heilprin also has shown that 

 in Yucatan there is an associated series of Pliocene and Pleistocene 

 limestones.^ 



1 Quart. Journ. Geol. Soc. vol. h (1895) p. 297. 

 ^ Proc. Acad. Nat. Sci. Philad. 1891, p. 141. 



