1871.] SENATE— No. 327. 15 



Besides the important addition of 2,417 mounted tablets to 

 our previous number, I have, in the process of re-arrangement, 

 found it necessary also to remount a very large number of the 

 species. This has been owing to the unsatisfactory nature of 

 the cement first used for the purpose, the very dry atmosphere 

 of our exhibition rooms operating unfavorably upon all the 

 cements known, at the time when we commenced this mode of 

 exhibiting shells. Much time and labor has been bestowed 

 upon this problem of the best cement for the purpose, and I am 

 happy to be able to say that I have so far succeeded in removing 

 all difficulties, that we may reasonably hope to be spared here- 

 after the time and labor of remounting, our present cement 

 seeming to be all that we could desire or expect. 



During the earlier portion of the year much of my time and 

 attention was given to our exchanges, which have continued to 

 increase in value and importance as a longer experience and a 

 better knowledge of the condition and wants of our collection 

 has enabled me to arrange with our numerous correspondents 

 for such species only as would supply deficiencies, and thus add 

 directly to our resources without, at the same time, burdening 

 ourselves with undesirable or unnecessary duplicates. 



Most of the specimens received during the year have been of 

 the most desirable and useful kind, and hence our collection 

 has increased both in value and importance in a much greater 

 ratio than ever before. By these exchanges we have received 

 from 27 contributors 40 packages of shells, containing 2,117 

 species and 15,853 specimens. These contributions have been 

 so uniformly good and so entirely acceptable that we cannot 

 well discriminate in favor of any one contributor, but would 

 render to all and each our unqualified thanks for their kind and 

 generous assistance. 



We cannot, however, omit to mention a few cases which, 

 owing to peculiar circumstances, have been to us of especial 

 value and interest. Thus, Mr. W. G. Binney, of Burlington, 

 New Jersey, sent us his entire stock of duplicates, which, hav- 

 ing been used by him in his many works on American shells, 

 comprised many species very desirable, not only for intrinsic 

 worth, but for collateral considerations, and has also already 

 been of service by furnishing unusual material for our ex- 

 changes. 



