EXPLANATION OF PLATE I. 



Figure 1. — Piunixa cyliudrica 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. — Platyouichus ocellatus Latreille, (j). 547 ;) male, slightly reduced in size. 



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



