BRANNER: THE STONE REEFS OF BRAZIL. 259 
Pectinia brasiliensis М. Edw. and Haime. 
Favia leptophylla Verrill. 
Калла gravida Verrill. 
Favia conferta Verrill. 
Acanthastraea braziliensis Verrill. 
Heliastraca aperta Verrill. 
Mussa harttia Verrill. 
Symphyllia harttii Verrill. 
Porites solida Verrill. 
OnpER, ALCYONARIA. 
Hymenogorgia quercifolia М. Edw. and Haime. 
Gorgomia (Pterogorgia) gracilis Verrill. 
Eunicea humilis M. Edw. and Haime. 
Plexaurella dichotoma Kölliker. 
Plexaurella anceps ? Kölliker. 
CLASS, ACALEPHAE. 
ORDER, HYDROIDEA. 
Millepora nitida Verrill. 
Millepora brasiliensis Verrill. 
Millepora alcicornis Linn., var. cellulosa Verrill, 
Millepora aleicornis Linn., var. digitata (?) Esper. 
Millepora aleicornis Linn., var. fenestrata Duch. and Mich. 
Thickness of the coral reefs of Brazil. — Near the rocky shores one can 
frequently see the thickness of the coral reefs, but these places do not 
help us to judge of the thickness of the same reefs a kilometre or two 
out at sea. It is evident from the physical conditions controlling the 
growth of coral reefs and from the shape of the submarine floor that the 
Brazilian reefs grow in the shallow waters along and upon the continental 
Shelf. Tt is not perfectly clear, however, whether this shelf may or may 
not have been built up in places from great depths by an upward growth 
of the reefs during periods of coastal depression. The contour of the 
bottom on which the reefs started was not necessarily alike in all places, 
80 that there is a chance for some local variation in the thickness of the 
ваше reefs, quite aside from any thickness attributable to the subsidence 
of the coast along which they grow. It is evident, however, that since 
Miocene times there has been an elevation of the coast that lifted the 
Marine Tertiary sediments out of the water and subjected them to ero- 
Sion both over the land surfaces and along the coast-line. Marine 
