CHAPTER XV. 



The collections upon which the following report and list are based were 

 placed in the hands of Mr. George W. Tryon, jr., Mr. W. G. Binney, Mr. Tem- 

 ple Prime, and Dr. James Lewis for determination, and it is to their kind- 

 ness that we are indebted, not only for the identifications given, but for 

 valuable notes in regard to the different species. To the latter gentleman 

 our thanks are due for a criticism and revision of the manuscript of this 

 report. 



A communication made by Mr. Tryon to the Academy of Natural 

 Sciences in regard to the collection of 1872 is by his permission appended to 

 the report, and it will be seen that some valuable facts in regard to the dis- 

 tribution of various genera have been evolved by this series of shells, small 

 though it may be. 



The collection of 1872 was made in Utah and Nevada, principally by 

 Mr. H. W. Henshaw and Dr. H. C. Yarrow, with the kind assistance of dif- 

 ferent members of the expedition; that of 1873, for the most part in Colo- 

 rado Territory, by Dr. J. T. Rothrock and Mr John Wolf, the botanists of 

 the expedition; and that of 1874, in Colorado, New Mexico, and Arizona, 

 by collectors of the expedition. 



Although we are able to chronicle but few discoveries, the report is 

 thought to possess a certain degree of value with regard to the limits 

 advanced of range and distribution. 



A tolerably abundant synonymy has been given, compiled from vari- 

 ous works on conchology, the principal of which are those of Messrs. Bin- 

 ney, Bland, and Tryon. 



The classification adopted is substantially in accordance with Prof. 

 Theodore Gill's " Arrangement of the Families of Mollusks", published by 

 the Smithsonian Institution in February, 1871, and to this gentlemen thanks 

 are also due for assistance and advice. 



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