12 



University of Michigan 



The pseudocardinals of the figure of the type of B. plexus 

 distinctus (C. and F., 1894) resemble the juvenile form, but 

 the description sounds more like those of the adult, in which 

 the posterior pseudocardinal of the right valve is very heavy, 

 jagged, and almost quadrate. 



Variation in E. plexus distinctui (C. and F.) 



Mean of 39 



specimens 75.0 64 41 



Extremes of lot 381094 60 to 72 33 to 48 



