JONES & BOBEBTS, 



Phil, Mag. Ser. 6, Vol. 20, PI. XIII. 



The Plates belonging to thin boo* are all 

 here but not in their proper places. 



Wo = 5 W,. 



rc 2 -rc, =200-6. 



Fig. 2. 





Am! 



Vwa\ 



^1A*WV 1 



/jfawvi 



IhN^S 



u' AkhfMkW 1 ! 





k=:*k 



w 2 -w 1 '=;i74-8. 



Fig. 3. 



