EXPLANATION OF PLATES. 



Enlargement, if any, of the figures is indicated by the fraction at the end of the 

 paragraph. LTnless so noted, the figure is of natural size. All specimens figured, 

 except as otherwise stated, are in the author's collection, now in the United States 

 National Museum. No effort has been made to orient the specimens in the usual 

 way with reference to the posterior side, which can not always be identified ; they 

 are posed rather with reference to the light in photographing. 



183081—21 5 59 



