branner: the stone reefs of brazil. 199 



Venus) which are as fresh and bright as the shells upon the present 

 beach. ^ These bivalves ai'e much sought for as food. They are taken 

 in the bays behind the reefs and near the shores, and also on sandbars. 

 Their dead shells are abundant on the present beaches. 



The Venus, so abundant in these rocks, lives in the sand ; but the 

 animals stand on end about five centimetres below the surface, and the 

 living shells are covered with horny epidermis. The shells found in 

 the rocks are always, so far as I have yet seen, without epidermis, the 

 valves are apart, and the shells usually have the convex side upward. 

 These facts show that the shells, as they occur in the rock, are not in 

 the places where the animals lived. 



Several other shells, mostly gasteropods, are found in the rocks of the 

 stone reefs, but wdthout exception they are forms that are often found 

 dead on the beach, or living in the shallow water near shore. 



The littoral character of the shells found in the reef rock should not 

 be overlooked, for Liais thinks some of the reef beds were formed at sea 

 {'^ forme cm milieu de la mer"), and that they have been displaced since 

 then. 2 



Barao de Capanema speaks of seeing fragments of pottery imbedded 

 in the rock near the lighthouse at Bahia.' 



Hartt thinks Pissis and Darwin " in all probability " mistook the stone 

 reefs for Tertiary rocks.* This seems to be an unwarranted assumption, 

 for in Pissis's paper there is no specific mention of the reef rocks,^ while 

 Darwin, in his paper on the Pernambuco reef, assigns to them a recent 

 date. 



Although one gets the impression that the fossils of the stone reefs are 

 all recent, the fact should not be overlooked that these fossils have 

 never been systematically studied in connection with the existing fauna. 

 Moreover, the reefs one sees, and to which access is easiest, are all the 

 new outer reefs, and usually the latest ones formed, while the old reefs 

 are to the landward, and usually near the bases of the hills that formed 

 the old shore lines. 



1 One sometimes hears the suggestion tliat the fresh colors of the reef fossils 

 is evidence of the recent age of tlie sandstone reefs. Tiiis may be true to some 

 extent, but these colors alone could not be accepted as evidence. We have rocks 

 of Jurassic age even, whose fossils still preserve their bright colors. 



2 L'Espace Celeste, p. 545, 548. 



8 Trabalhos da Commissao Scientifica de E.xplora^ao. Rio de Janeiro, 1865. 

 Introduc(;ao, I., p. CXXXVII. 

 ■» Geol. and Phys. Geog., p. 269. 

 6 Mem. Inst. France, 1842. X., p. 308. 



