BIOLOGICAL BULLETIN, VOL. XLVI. 



PLATE I. 



_ - , 



. 



^ 



- 





7 



. 5 



v . 



8 



* . 





10 



i 







F 



x . 



11 



12 



^ 



13 



15 



C. W. METZ AND J. F. NONIOEZ 



