l8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I23 



ravalliensis. F. is less than two times as long as broad (average length 

 124 microns, width 67 microns), usually with area of greatest width 

 above middle, though in some specimens F. is hemispherical in outline 



Figs. 38-42. — Peromyscopsylla ebrighti: 38, Genal area, d*; 39, eighth sternum, 

 (5"; 40, seventh sternum and spermatheca, ?; 41, immovable process and digitoid 

 of male clasper ; 42, distal arm of ninth sternum, c?. For explanation of symbols 

 see pages 67-68. 



(figs. 29-31). It will be seen that the shape of F. is quite variable, 

 and all variations were found in a single collection from Peromyscus, 

 Nye County, Nev. A series of paratypes of P. hemisphaerium fall 

 well within this range of variation. The female is distinguished from 

 the other subspecies (except hesperomys ravalliensis) by the shape 



