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LEDA (HEBELSM) BOvrDSTTIAIIA var. SUBTmilDA n. Ysr, 



Description ,- Shell resemlDling the typical bowdeniana. hut 

 more elongate, slightly less convex; umhones lower and less 

 tumid; ventral raarprin less curved; sculpture coarser and more 

 irregular; chondrophore hroader; hinge with about sixteen teeth 

 in each series, the anterior series more convex and the posterior 

 less concave than in the tj-pieal bowdeniana . 



Di.nensions .- length, 6.5 mm.; alt., 4 mm.; semidiam. , 1,7 nm. 



Remarks .- A number of valves are inc^'uded ujider this var- 

 iety. '.Then coranared vrith bowdeniana they show the above diff- 

 erences, which, though slight, involve many characers and are 

 constant. Since the variety is more elongate and has lower 

 umbones, it follows that the slope of the dorssl margins is less 

 steep and the postero-dorsal margin less excavated. 



A poorly preserved shell which is higher than the typical 

 bowdeniana and has a shorter rostrum and obscure concentric sculp- 

 ture which is obsolete on the posterior half of the shell, prob- 

 ably indicates a tendency to variation in a direction antipodal 

 to subtximida . 



Occurrence.- lov/er lliocene : Boxvden beds. Bow den, Jamaica. 



