bartsch: northwest coast mollusks 565 



gen sulphide or with the precipitation of atomic sulphur. In 

 such a water, therefore, the number of bicarbonate ions is grad- 

 ually decreasing as the number of the hydroxyl ions is increasing. 

 The acidity of calcium and magnesium chlorides toward the 

 alkaline sulphides is pronounced but has less effect on the bi- 

 carbonates. 



Although the addition of a few cubic centimeters of neutral 

 barium chloride solution to an ordinary carbonate water aids in 

 breaking up the bicarbonate ions, it has no such effect if the 

 water contains a considerable quantity of alkaline sulphides. 



Hydrogen sulphide is volatilized much quicker and more com- 

 pletely at boiling than at room temperature, but a certain per- 

 centage is not expelled by a rapid current of hydrogen even after 

 one or two hours. 



A discussion of the reduction of sulphates by organic matter 

 has been published by C. E. Siebenthal.^ The author has been 

 able to produce noticeable amounts of H2S in a hydrogen gener- 

 atorcontaining about 20 per cent H2SO4, about 0.5 gm. NaCl, 

 some KI and SnCl2, some CaS04 and organic matter derived 

 from the oxidation of fruit in nitrosulphuric acid. The H2S was 

 sufficiently strong to mask the Gutzeit test made for arsenic. 



Acknowledgment is due to Dr. Chase Palmer, recently of the 

 United States Geological Survey, at whose suggestion and with 

 whose cooperation this work was undertaken and carried out. 



CONCHOLOGY. — The Caecidae and other marine mollusks from 

 the northwest coast of America.'^ Paul Bartsch, U. S. 

 National Museum. 



The "Summary of the Marine Shell Bearing Mollusks of the 

 Northwest Coast of America," by Dr. William H. Dall, about to 

 be published by the U. S. National Museum as Bulletin 112, 

 contains references to a number of species, of which no descrip- 



2 U. S. Geol. Survey Bull. 606: 62-66. 1916. 



1 Published by permission of the Secretary of the Smithsonian Institution. Re- 

 ceived October 22, 1920. 



