334 DR. G. J. HINDE. 



fragmentary materials largely consist of foraminifera and organic debris, with only a 

 small proportion of corals. As mentioned above, the corals in the boring below 

 180 feet have been greatly altered and reduced to mere casts, some of which are so 

 friable that they can be crushed between the fingers. Fragments of such casts are 

 present in the broken-up rock, and it seems highly probable that the fragile nature 

 of the rock in this part of the boring may result from the destructive changes in the 

 corals. But judging from the solid cores which have been preserved, the foraminifera 

 and fragmental organic debris would form a still greater proportion of the rock than 

 in the 150 feet above. The rock of the lower part of this division between 640 feet 

 and 748 feet is generally friable, porous, and chalky-looking, coral casts are more 

 numerous in it, Halimeda is abundant, and the cementing material is dolomite, thus 

 showing a gradual passage into the rock below. 



The corals recognised belong to twenty-eight genera ; with one exception they are 

 present in this Main Boring. They all belong to well-known reef-building forms, 

 and most of them still exist on the reef and in the lagoon at Funafuti. Of the 

 foraminifera forty-one genera have been determined, thirty-five of which occur in 

 the Main Boring. Only seven of these genera are of significance as rock formers, 

 and, like the corals, they are still flourishing on the present reef or in the lagoon. 



Although there are considerable differences in the character of the rock in different 

 parts of the Main Boring, the evidence appears to me to indicate a continuous 

 formation of reef rock, without any abrupt break, from the depth of 1114 feet to the 

 present time. 



In the borings beneath the floor of the lagoon, the rock for a distance of about 

 70 feet consisted principally of the joints of Halimeda with a small proportion of 

 foraminifera ; these materials were quite loose and not cemented together in any way. 

 Between 70 feet and the bottom of the boring at 144 feet the rock is a rubbly 

 limestone cemented by calcite, in which Halimeda diminishes and is replaced by 

 corals and foraminifera of the same kinds as those in the upper part of the Main 

 Boring. The organisms are, as a rule, well preserved, and their structures are, if 

 anything, better shown than those at corresponding depths of the Main Boring. 



