THE NAUTILUS. 105 



where the water disappeared, was a series of clear, rather deep 

 pools, called '' water holes," connected by a tiny, clear rivulet. 

 In one of these pools was collected that year the type lot of 

 Sphaerium hendersoni Sterki. Then came the "boom" in dry 

 lands in Eastern Colorado. Scores of small tracts of prairie 

 sod, many of them on steep slopes, were broken by the settler's 

 plow. The dry soil, no longer held together by the sod, ws 

 carried into the valley by summer storms, filling many of the 

 pools and depositing a thick coat of mud over the whole stream 

 bed. In June, 1912, I revisited the locality, and found no 

 clear water at all, and not a single mollusk of any species. The 

 sluggish stream carried a heavy load of silt so fine it would not 

 settle. Probably the Sphaerium is extinct at the type locality. 

 It is likely that innumerable changes in the faunas of the 

 West are occurring as a result of the settlement of the country 

 and consequent changes in environment. This is known to be 

 true of birds and mammals. For this reason it is desirable that 

 biological work in this vast region be pushed as rapidly as pos- 

 sible, to provide data for future estimates of biological changes. 



NOTES. 



HODGSON COLLECTION. I have just secured the collection of 

 the late Chas. S. Hodgson, containing some 2500 to 3000 

 species, a few fossils and books. Besides his work in Illinois 

 he did considerable collecting in other places and added to the 

 collection by exchange and purchase. A. A. HINKLEY. 



DR. G. DALLAS HANNA, who for eight years has been an 

 assistant in the United States Bureau of Fisheries, has been ap- 

 pointed curator of invertebrate paleontology in the California 

 Academy of Sciences. Dr. Hanna has for seven seasons been 

 engaged in scientific work on the Pribilof Islands, Alaska, hav- 

 ing taken the census of the fur seal herd for five consecutive 

 years. He brings to the museum of the Academy his collection 

 of mollusks which numbers about 100,000 specimens. 



FLUKE IN PHILOMYCUS. It may be of interest to the readers 



