Am. Jour. Sci., Vol, XLVIII, 1S 



Plate X. 



.Pt 



1VI 



_-/Ni 



.-^r 



x 



/ : -!3 

 /-Zi 



/-Hg' 



:-AtI 



6>AltJ 



<-H 2 0' 



1 2 3 4 5 G 7 



9 10 11 U 13 14 15 16 17 



