EXPLANATION OF PLATE I. 



Figure 1. — Pinnisa cylindrica Say, (p. 546 '^ male, enlarged four diameters. 

 2.— Pinnotheres ostreum Say, (p. 546 ;) male, enlarged four diameters. 

 3.— Panopeus depressus Smith, (p. 547 ;) male, natural size. 

 4. — Platyonichus ocellatus Latreille, (p. 547 ;) male, slightly reduced in size. 



<A11 the figures were drawn by <J. H. Eraerton.) 



