92 THE NAUTILUS. 



THE MISSOUBI BIVEB AS A FATJNAL BABBIEB. 



BY PAUL BART8CH. 



Several years ago I published a note in "Science" on this 

 topic. It seems that this has not come to the attention of most 

 of the workers who are dealing with fresh-water pearly mussels, 

 and I therefore deem it wise to again call attention to it. 



In our work during the Mississippi Valley Pearl Mussel In- 

 quiry, we found that the enormous amount of sediment carried 

 by the Missouri River formed an effectual barrier to the distri- 

 bution of the Unionidae. There, while the Mississippi and its 

 tributaries to the north of the Missouri River teemed with 

 aquatic life, careful search in the Mississippi below the mouth 

 of the Missouri, and the mouth of the Ohio, did not reveal a 

 single living Unionid. Dead specimens were also absent on the 

 sand bars south of St. Louis. The heavy load of mud carried 

 by the waters of the Missouri, yielding f inches of sediment in 

 a three-inch tube, probably strangles these and other organisms. 



We have, therefore, the curious condition of a river forming 

 a barrier to aquatic animals. 



SHELL COLLECTING IN THE SIERRA NEVADAS. 



BY HERBERT N. LOWE. 



To see the Yosemite and the groves of Giant Sequoias had 

 been a dream long cherished during my thirty years residence 

 in California. Some dreams come true ; and this summer my 

 mother and I drove there, with our " Buick Six" well stocked 

 with camp outfit. 



The early part of September is rather a dry and unpropitious 

 time for collecting mollusks in the mountains. Rock piles and 

 moist meadows were the most favorable stations. These lovely 

 Sierra meadows, filled with brilliant wild-flowers and sur- 

 rounded by noble forests of pine, cedar and fir, are the most 

 charming spots imaginable. One vainly hunts for words to give 

 an idea of the wonderful scenery of the Sierra Nevadas. Each 

 day was simply perfect, with clear warm sunshine and air sweet 



