lii 10- 



o s 5 



RIGHT VALVE 



"20 25 30 35 3o Ji 15 55 io 65 ?0 

 VALVE HEIGHT (MM.) 



|20i LEFT VALVE 



S < IS- 



IS 20 25 30 35 40 45 50 55 60 65 TO 

 VALVE HEIGHT (MM.) 



L.blQCki 



CONVEXITY OF LEFT VALVE (MM.). 



Fig. 16. — A, Ontogeny of the muscle scar in Lopha hellaplicata bellaplicata 

 (Shumard), showing relationship between maximum diameter of the posterior 

 adductor muscle scar and the height of the valve. Note the decline and virtual 

 cessation of scar growth with increased size and age. Approximate boundaries 

 between ontogenetic stages marked by dashed lines. E = Ephebic ; T = Ephebic- 

 Gerontic transition ; G = Gerontic. B, Comparison of the plication density of 

 Lopha bellaplicata bellaplicata with that of L. blacki (White), showing total 

 overlap of the two forms. C, Comparison of the relative convexity of L. bella- 

 plicata bellaplicata and L. blacki, showing nearly total overlap between the two 

 forms. 



52 



