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SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO3 



angles with the top plates, flush with and on each side of the slot 

 and contiguous with the lateral pieces to which they are cemented. 

 The space between the slides from the ends of the lateral pieces to 

 the longitudinal free margins of the slides (a distance equal to the 

 thickness of the top plates) is filled by a strip of appropriate width 

 cut the full length of a slide and cemented in place to form the floor 

 of the slot. If preferred, a strip of hard wood, to cushion the points 

 of the pins, may be substituted here for glass. The slot depth, from 

 the free surface of the top plates to the inner edge of the bottom 

 strip, now measures the width of a microscope slide (about i inch) 



Rg. 5 

 A slotted pinning block in process of construction. 



and gauges the correct position for slips bearing medium to small 

 beetles on the standard 34-mm. (i|-inch) pin. Additional gauges for 

 lower levels of the mounting slip, as well as for pin-label heights, 

 may be had simply by inserting small removable glass rectangles of 

 the proper widths at the ends of the slots, an operation which had 

 best be performed after the block is otherwise completed. The glass 

 assemblage is now placed, top downward, in the center of the mold 

 and mixed plaster of paris poured over it to a depth greater than the 

 walls of the slot (fig. 5). 



A slotted pinning block makes it possible to pin mounting slips 

 squarely with reference to the transverse axis, yet with the longitudi- 

 nal axis at a slight angle to the horizontal. It is advisable, when 

 pinning heavy mounts, to tilt them slightly upward in front in order 

 to compensate for gravity, and to strengthen them by means of a 

 drop of cement placed so as to embrace the pin at its point of exit. 



