1918.] 



NATURAL SCIENCES OF PHILADELPHIA. 



91 



X 





rdl 



lit 



Ivs 





m'-Lm 



rll 

 mt 



ret 



Idrti K^ 



Idt 



cm 



pe 



vim 



ret 



- rdt 



rlrti 



mt 



~ vim 



III 



nc 



rll 



