636 7^he Smithsonian Institution 



guished by being printed in capitals, and are followed by 

 statements of chemical composition and crystalline form, and 

 by lists of synonyms and varieties. 



G. W. Hawes (Proceedings, Volume iv) shows that the 

 Triassic diabases of the eastern United States contain not 

 only labradorite, but various other feldspars, among which are 

 andesine, anorthite, and albite. He also calls attention to the 

 frequent absence of twinning structure in the triclinic feld- 

 spars, and the consequent unreliability of optical determina- 

 tions not checked by chemical analysis. 



G. P. Merrill has published numerous papers on mineral- 

 ogical and lithological subjects in the " Proceedings of the 

 National Museum." Among them is one somewhat elaborate 

 paper entitled, " Notes on Some Eruptive Rocks from Galla- 

 tin, Jefferson, and Madison Counties, Montana" (Volume xvn). 

 In several notes on " Serpentines," from various localities (Vol- 

 umes xi, xn), evidence is given of the derivation of serpentine 

 from olivine and other anhydrous magnesian silicates. The 

 glistening surfaces, like slickensides, in the serpentines, are 

 attributed to the friction of movements due to the expansion 

 of the mass in undergoing hydration. Interesting studies on 

 points of detail in geological structure are given in notes 

 " On Fulgurites " (Volume ix), " On Stalactites and Gypsum 

 Incrustations," and on "Sandstone Concretions" (Volume 

 xvn). A note " On Deposits of Volcanic Dust and Sand 

 in Southwestern Nebraska" (Volume viu) records the first 

 known observation of unaltered volcanic ashes or tufa in the 

 United States east of the Rocky Mountains. 



C. T. Simpson discusses (Volume xvi) the Unios found in 

 the deposits near Toronto supposed to be interglacial. All 

 are species belonging to the fauna of the Mississippi Valley, 

 and most of them are no longer found in Canada. Their in- 

 troduction into the drainage basin of the St. Lawrence dates 



