244 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



reef of sandstone. This particular reef is eight hundred metres long, 

 not including some detached fragments lying beyond its southern end, 

 and not shown on the map herewith, which would give it a total length 

 of something more than a kilometre. 



" A fact of unusual interest in regard to this bit of reef is that it 

 overlies a dead cored reef. The overlap is plainly visible at many places 

 where re-euti'ant angles have notched the stone reef, or where large frag- 

 ments have been left isolated but fast to the coral reef. The coral reef 

 visible here at low tide is from one hundred to two hundred and seventy 

 metres wide, measured from the outer margin to where it is overlapped 

 by the stone reef or by the beach sands. This coral reef is almost per- 

 fectly flat and level. Not a single living coral could be found on its 

 upper surface ; the coral most abundant in the rock itself is Porites. 



" Outside or seaward of this reef is still another coral reef with which 

 the inner one is not connected, at the water's snrfjxce .at least. 



nrrnTTFrf^ 



Fig. 57. Section across the stone and coral reefs at Sapucahy. The vertical 

 shading on the right represents the coral reef. 



" The sandstone reef lies at a higher level on the beach than the coral 

 reef, and has throughout most of its length a decided seaward dip. At 

 the southern end of its contact with the beach, howevei*, the dip is re- 

 versed and the bedding looks very much as if it had been formed by 

 sand washed over and behind a low beach or spit. The rock is in some 

 places rather soft, in others it is quite hard and rings when struck with 

 the hammer." 



At Paripueira and southward the coral rocks are exposed at the lowest 

 tides in many places and over large areas. At .this place there is a 

 considerable business in the burning of coral rock for lime.^ 



Off the mouth of Eio Pioquinho there are at least three coral reefs, 

 the one nearest shore being three hundred metres out from the beach. 

 Off the sandy point near Pioca there is one coral reef one hundred and 

 fifty metres out from the beach, and the interval contains many isolated 

 points of coral rock, while outside is a second reef about four hundred 

 metres from the beach. These reefs are broken in front of the bay just 



^ The extraction of these rocks in the State of Alagoas is under the supervision 

 of the Captain of the Port at Maceio, and tlie burners are taxed by the govern- 

 ment in proportion to the size of the kilns burned. 



