DEPARTMENT OF MOLLUSKS. 175 



The mere piling up or acciimulation of named, labeled, and classified 

 shells is, of itself, of value only to the person who goes through with 

 the mental and i)hysical exertion it requires. To justify the existence 

 of a public museum it is generally admitted it must do more than this. 



In the Department of Mollusks the following objects are steadily kept 

 in view, and the progress made is directly or indirectly instrumeutal 

 toward the attainment of them : 



(1) The preservation of types which have served for previous study 

 as a means of verifying the accuracy of past work or the proper orien- 

 tation of new researches. 



(2) The full representation of American forms in the study collection; 

 not only that the fauna of our own country may be fully known but 

 for ease in assisting American students to recognize the forms of their 

 local collections, and for the benefit of the foreign student, who may 

 thus make his comparisons or researches in one place with the least ex- 

 penditure of time, travel, and expense. 



Under the two i)revious heads the Biuney collection of North Ameri- 

 can land shells has been arranged in a special case, numbered and 

 arranged to correspond with the last publication on the subject by Mr. 

 Binney. 



Considerable progress has been made with the other American land 

 shells, and the present year will certainly see our collections of this 

 sort in complete order for ready reference by the naturalist or paleon- 

 tologist. 



(3) The instruction and entertainment of the iiublic, who, drawn by 

 curiosity or the love of beautiful and unusual objects, come to view the 

 contents of the Museum which are on exhibition. 



The curator has been convinced by past experience that to be useful 

 to the general public a collection of biologic material should not be too 

 large, should be arranged on as simple a plan as can be devised, and 

 should have as many and as large legible labels as is consistent with 

 the i)roper visibility of the objects in the case. 



If the cases for exhibition can be so filled and arranged as to teach a 

 lesson which he who runs may read, it is my opinion that they come 

 near doing their best possible work for the average visitor. 



In this view the cases devoted to the shell exhibit are for the passer 

 by and not for the student, unless a beginner. One case arranged by 

 the curator has been devoted to the cKef types of Oephalopods, to 

 pearls and pearl formations, cameo shell and sections showing the inter- 

 nal structure of various large and ornamental species. The sections of 

 the recent and the fossil Nautiloids are put side by side. Specimens of 

 the SpiruJa, Loligo, Sepia, etc., in alcohol fully labeled, alternate with 

 stands on whicli are mounted the shelly parts of the same genus. 



The various shells which produce jiearls stand by the side of the 

 pearl itself mounted in a vertical tube with a hemispherical end, 



