1884.] 29 [Bouve\ 



The olivine is in irregular fissured grains usually surrounded 

 by or adjacent to the augite, but it is occassionally observed en- 

 tirely surrounded by feldspar. Frequently along the fissures it is 

 filled with magnetite or by a greenish serpentineous product. 

 It further contains inclusions of feldspar, magnetite, pyrite, etc. 



The magnetite is in irregular grains generally surrounded by a 

 border of secondary biotite or hornblende. It is associated with 

 and frequently surrounds the pyrite. 



Similar rocks have been described by Mr. G. P. Merrill in the 

 Proceedings of the National Museum, 1883, vi, 176, 177. 



Mr. S. Garman showed a very remarkable selachian from 

 Japan, which he had described under the name of Chlamydose- 

 lachus anguineus. 1 



General Meeting, February 6, 1884. 



The President, S. H. Scudder, in the chair. Twenty-nine per- 

 sons present. 



The following papers were read : — 



THE GENESIS OF THE BOSTON BASIN AND ITS ROCK FOR. 



MATION. 



BY THOMAS T. BOUVE. 

 Hi 



The paper upon the conglomerate and the slate of this neigh- 

 borhood read at our last meeting by Mr. Crosby, and the pro- 

 longed discussion which followed participated in by Dr. Wads- 

 worth, Prof. Niles, and myself have led me to present some views 

 upon the Boston basin of a more comprehensive character than 

 such as deal only with the relative age of the rock-formations 

 contained in it, as it is possible that a study of the probable ori- 

 gin of the basin itself and the consequent phenomena, may throw 



1 Science, vol. in, 116. Bull. Essex Inst. vol. xvi. 



