BRANNER: THE STONE REEFS OF BRAZIL. 259 



Pedinia Iradliensis M. Edw. and Haime. 



Favia leptophylla Verrill. 



Favia gravida Verrill. 



Favia conferta Verrill. 



Acanthastraea braziliensis Verrill. 



Heliastraea aperta Verrill. 



Mussa harttii Verrill. 



Symphyllia harttii Verrill. 



Porites solida Verrill. 



Order, ALCYOXARIA. 



Hymenoyorgia quercifolia M. Edw. and Haime. 

 Gorgonia (Pterogorgia) gracilis Verrill. 

 Eunicea humilis M. Edw. and Haime. 

 Plexaurella dichotoma Kolliker, 

 Plexaurella anceps ? Kolliker. 



Class, ACALEPHAE. 

 Order, HYDROIDEA. 



Millepora nitida Verrill. 



Millepora brasiliensis Verrill. 



Millepora alcicornis Linn., var. cellulosa Verrill. 



Millepora alcicornis Linn., var. digitata (?) Esper. 



Millepora alcicornis Linn., vav. fenestrata Duch. and Mich. 



Thickness of the coral reefs of Brazil. — Xear 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. It is not perfectly clear, however, whether this shelf may or may 

 not have been bnilt up in places from great depths by an upward gi-owth 

 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, 

 so that there is a chance for some local variation in the thickness of the 

 same 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 



