MOLLUSCA OF MICHIGAN— WALKER. 



453 



the number on the shell in ink. Then, if a drawer happens to be over- 

 turned, the specimens can be sorted out again without difficulty. 



When numbered, the vials and specimens should be placed in trays. For 

 these a standard size should be adopted, so that they will conveniently 

 fit into the drawers of the cabinet. In the National Museum at Washington, ■ 

 the unit is 1 x 2 inches, and the larger sizes are all multiples of that unit. 

 In the Academy of Natural Sciences at Philadelphia the unit is 1 x 3 inches. 

 In either case a convenient intermediate size is H x 2 or 3, as the case may 

 be. There is one advantage in the use of the larger unit where space is a 

 serious question. For the small species the vials may be used only IJ 

 inches in length, and two vials can be put into one tray, thus doubling the 

 capacity of the drawer. The trays should be of the same depth. One- 

 half inch is sufficient for most of the univalve species. For the larger spe- 

 cies and the Unionidce, requiring trays of good size, f inch is better. These 

 trays can be had of any paper box manufacturer, or can be easily cut out 

 of cardboard by the collector, the corners being fastened together by strips 

 of gummed paper. The character of the cases for a collection is deter- 

 mined by the means and inclination of the collector. Any case of shallow 

 drawers will do. If, however, cases are to be made, they should be made of 

 a standard size with interchangeable drawers. The standard drawer should 

 be one inch in depth on the outside. The length and width may be of any 

 size, provided they are always the same; 19 x 19 inches inside measurement 

 is a convenient size for a case with two rows of drawers. Other drawers 

 may be 2 inches or 3 inches in depth, but comparatively few of the latter 

 size will be required. The cases may be of any height desired, according to 

 the number of drawers needed. The method of hanging the drawers is as 

 follows: On the inside of the cases are fastened a series of horizontal cleats 

 one inch in depth and | in width at the broad end, extending from the top 

 to the bottom. The following diagram will show the arrangement: 



In the one-inch drawers the entire outer edge is beveled to fit the angle 

 of the cleat, and the drawer runs on the projecting edge. In the other drawers 

 a projecting rail is set into the side one inch from the top of the drawer, 



