Bull., U. vS. B. F., 1919-20. 



Plate X\'II. 



Fig. 2. — A young inussel. Syvt/jhynola 

 cosiata, six days after completing the 

 stage of parasitism. (Lefevre and 

 Curtis. ) 



Fig. I. — Glochidium oiSymphyih-ia noslaia in process of transformation 

 during stage of parasitism. (Lefevre and Curtis.) 



\ 



Fig. .1. — A young squaw-foot mussel, Stropliilits edcntulus, which had 

 completed metamorphosis without parasitism; showing two adduc- 

 tormussels, foot, gills, and rudiments of other organs of adult mussel, 

 (Lefevre and Curtis.) 



Fig. 4. — A young muckel, LamPsilis 

 liganicnthia, a week after the close of 

 the parasitic period. ( Lefevre and 

 Curtis.) 



