548 H. B. GUPPY ON THE RECENT 



Additional List (relative frequency not ascertained). 



Cassidulina crassa. 

 Bulimina niarginata, 

 Uvigerina pygmsea. 

 Nodosaria soluta. 

 Globigeriua sacculifera. 



Pulvinuliua elegans. 



,, canadensis. 



„ menardii var. fimbriate. 



,, repanda. 

 Tnmcatulina sp. 



This formation displays regular bedding, the beds being in some localities 

 separated by thin bands, one to two inches thick, of a loose coarser-grained deposit 

 of the same nature.* Having explored most of the principal streams, which are 

 mostly confined to the west side of the island, I have shown the main results in 

 the accompanying plan of Ugi (Plate CXLIV. fig. 1) ; whilst the ideal section 

 (Plate CXLIV. fig. 2), which actually represents a section through the south por- 

 tion of the island, will serve to illustrate the structural features, more particularly 

 the curvature of the beds and the comparative thinness of the crust of coral rock. 

 The tortuosity of the streams, with other circumstances, combined to hinder 

 my efforts to arrive at a satisfactory explanation of the lie of the beds ; and 

 it was only after repeated tedious examinations of these stream-courses that I 

 was able to reduce my observations to order. The clip varies usually between 

 10° and 15°, but it may rise to as much as 35°. In the higher parts of the island, 

 near the sources of the streams, the beds are generally horizontal or very gently 

 inclined. By referring to the plan of the island, where the arrows indicate the 

 direction of the dip, it will be seen that the prevailing trend of the folds is 

 N.E. to S.W. ; but in the northern part of the island they run more N.W. to 

 8.E. Although the series of curves into which these beds have been thrown 

 are generally regular, yet the occasional sudden increase of the dip and the 

 occurrence of local contortions are circumstances which afford evidence of the 

 minor disturbances to which these beds have been subjected. The natural 

 sections displayed in the sides of the ravines and gorges vary considerably in 

 different streams, and in different parts of the same stream ; most frequently, 

 however, the stream appeared to have run along the crest of an anticlinal 

 ridge. I should here allude to a common feature of these stream-courses, 

 as well as of those of Treasury Island, viz., the extensive deposits of cal- 

 careous tufa which frequently encrust the sides of the gorges and constitute 

 a series of step-like terraces over which the water flows in the higher parts of 

 some of the streams ; leaves, twigs, and shells are often thus imbedded. 



I carefully searched these beds for enclosed organic remains in addition to 

 the minute organisms there imbedded. Entire shells are rarely found, those 

 referred to in the description of the composition of these rocks being the fine 

 fragments of Lamellibranchiate and Gasteropod shells. I only came upon five 



* In a limited locality in the south part of the island the rock was a very fine grained calcareoui 

 tuffa, containing a few siliceous marine organisms. 



