Plati: 111 ; Figs. 17 to 21 ; Ar.r, Magnified 500 Diami:ti-:rs. 



Difflir^ia /^yrifonnis l*erty p. 15 



Xitclcan'a simplex Cienk p. 18 



DifHiii:;ia cratera Loidy p. 15 



Ouadntia sxiiniictrica Ehv , .p. 15 



Microj^roiiiia (?) p. i(^ 



