PLATE XXIV. 



Fig. l. Gemma purpurca var. Tottcni Stm., from above ; 3.5 mm. 



Fig. 2. Gemma purpurca Lea, right valve, from above; 2.8 mm. 



Fig. 3. Gemma purpurca var. Tottcni Stm., side view ; 3.5mm. 



Fig. 4. Gemma purpurca Lea, side view ; 2.8 mm. 



Fig. 4b. Gemma purpurca Lea, interior of right valve ; 2.8 mm. 



Fig. 5. Carolia floridana Dall, view of the cardinal region showing valves in juxta- 

 position ; p. 777. 



Fig. 6. Carolia floridana Dall, from above ; no mm. ; p. 777. 



Fig. 6 b. Carolia floridana Dall, profile of part of the lower valve showing scar of 

 foramen and profile of chondrophorus ; p. 777. 



Fig. 7. Carolia fl.oridana Dall, view of the same from above. 



Fig. 7 b. Carolia floridana Dall, showing interior of upper valve, cardinal areas, liga- 

 mentary and adductor scars ; 1 10 mm. ; p. 777. 



Fig. 8. Aligena aquata Conrad, sp., Miocene of Virginia; interior of the left valve; 

 5 mm. 



Fig. 8 a. Aligena a-quata Conrad, sp., showing exterior of left valve ; 5 mm. 



Fig. 8 b. Aligena cequata Conrad, sp., showing interior of right valve ; 7 mm. 



Fig. 9. Plcurodon Adamsii Dall, interior of right valve ; 3.25 mm. ; Florida Strait ; 

 figured for comparison ; p. 60 1. 



Fig. 10. Pleitrodon Woodii Dall ; 2.75 mm. ; p. 600. 



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