| 
| 
| 
| 
BRANNER: THE STONE REEFS OF BRAZIL. 163 
Fra. 91. Section at the village of São Thomé. 
Савв III. Trachytic boulders (see р. 159). 
Hypothesis Г. 
The burrows would have to be 
made before the greater elevation, and 
the following depression would bring 
them within the reach of the water. 
Hypothesis IT, 
The rocks were carried beneath the 
water by the depression, then bur- 
rowed, and later slightly elevated. 
Ес. 02, Trachyte blocks bored by sea-urchins. 
Case IV. has reference to the eroded coral reefs (see pp. 239-245). 
Hypothesis I. 
Greater elevation would either have 
to take place before the reefs were 
made, or else the reefs would all be 
killed by the elevation. The depres- 
sion would put them back in the 
water, 
Hypothesis IT. 
The depression would permit corals 
to grow up to a depth of 150”; а small 
elevation, when they were already 
near the surface, would kill them and 
allow them to be eroded. 
Case У. is that of the terrace at Ilheos spoken of on pp. 153-155. 
Hypothesis I. 
Necessitates the formation of the 
terrace before the elevation, and a 
subsequent depression, 
Hypothesis IT. 
The terrace was made during the 
depression, and lifted by a small 
elevation. 
