E. W. Berry — Potamogeton from. Upper Crefaeeous. 423 



have an extended, and many a cosmopolitan range. Thus 

 Potamogeton perfoliatus Linne extends over more than 

 twenty degrees of latitude in North America and is found 

 also in Europe and Asia. 



All of the wide ranging forms extend into both high 

 and low latitudes whereas species of restricted range are 

 commonly confined to warm regions. Climate is less of 

 a factor in aquatic than in terrestrial vegetation, but in 

 spite of this it would appear that the giaciation of the 

 Pleistocene in the lands of the Northern Hemisphere was 

 one of the factors in extending the range of the present 

 wide ranging forms, and that these are geologically older 

 than those species of restricted range. 



The Johns Hopkins University, 

 Baltimore, Md. 



Art. XXIX. — Additional Notes on the Crystallography 

 and Composition of Boulangerite; by Eael V. Shan- 

 non.^ 



Existing knowledge of the crystal form of boulangerite 

 rests almost entirely upon the work of Sjogren^ upon 

 material from Sala, Sweden, which showed the composi- 

 tion of this mineral to be different from the formula 

 usually given and endeavored to show its relation, both 

 chemical and crystallographic, to diaphorite. The present 

 writer has recently published a paper on the chemical 

 composition of this mineral with 8 new analyses made 

 upon material from various localities which apparently 

 confirm Sjogren's conclusions relative to its composition.^ 

 Additional study of one of the specimens analyzed has 

 shown the presence of measurable crystals which have 

 been made the subject of the following notes. The exact 

 history of the specimen is somewhat uncertain but it is 

 known to be from the Wood River district in Blaine 

 County, Idaho and it is probably from the Independence 

 mine. An analysis of the material is given in the publi- 

 cation above cited. The crystals occur as small rosettes 



^ Published by permission of the Secretary of the Smithsonian Institution. 

 * Geol. Foren. Forhandl., 19, 153-67, 1897. 

 ^ Proe. TJ. S. Xat. Mus., 58. 5S9-59S, 1920. 



