EXPLANATION OF PLATES 



All figures, except those upon Plates A, B, C, and XXI, unless otherwise noted, are made 

 from light prints of photographs direct from the specimens, finished with India ink brush 

 drawings. They are reproduced by the heliotype process. Enlargements, if any, are indi- 

 cated by an improper fraction placed at the right lower corner of each figure ; if not so 

 distinguished the figure is of natural size. Figures of each specimen have a common serial 

 number, different views being designated by a small letter after the number. If but one figure 

 is given, it bears a number without lettering; thus "fig. 3" indicates that there is no other 

 view of that sj^ecimen, while "3a''' shows that one or more other views are given. All 

 specimens not otherwise noted are in the author's collection, now at the United States National 

 Museum, Washington, D. C. 



