MARYLAND GEOLOGICAL SURVEY 



147 



GEOLOGICAL DISTRIBUTION OF SPECIES. 



SPECIES. 



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in Rangia cuneata (Gray) which is found only at the present time in 

 the Gulf of Mexico from Alabama to Vera Cruz, Mexico. This species 

 occurs in the Pliocene of the Carolinas and Florida and may have had a 

 much more northern range during that period, living even to the north- 

 ward of Maryland. Its occurrence, therefore, in the Maryland Pleisto- 

 cene may really represent a stage of gradual restriction to more southern 

 waters. Leda acuta (Conrad) is likewise a characteristic southern spe- 

 cies, being common along the southern coast of the United States. 



