26 BUIXKTIN 27 



strong, numerous, subequal, concentric lamellose lines ; on this 

 area, the pustules are lacking or if present very small and incon- 

 spicuous ; anteriorly the concentric sculpture is less strong and 

 quite irregular ; a radial sculpture is present, consisting of rais- 

 ed irregular strise which may break up into numerous, small, 

 nearly continuous pustules on approaching the basal margin ; 

 other characters similiar to the type form. 

 Height. 7.5, width 8 vim. 

 Four specimens of this shell from Jones Wharf, Maryland, 

 all show the above characters, differenting them from the typical 

 A. pustulosa Dall. In their shape, strong carina and in other 

 general features, the shells agree with their Oligocene precursor. 

 Choptank formatio?i ; Jones Wharf, Md. 



Lithophaga pectinieola, n. sp., Palte 3, Fig. 2 



Shell elongate, subcylindrical, thin and fragile ; with the 

 dorsal and ventral sides straight, and nearly parallel ; beak 

 nearly terminal ; anterior end well rounded, posterior produc- 

 ed and obtusely pointed ; external surface smooth with the 

 growth lines faint ; the surface is in addition quite strongly 

 marked with regular resting stages, most evident on the post- 

 erior slope. 



Length 12, height 4. mm. 



The type specimen was found in a large Pecten shell from 

 Yorktown, Va. It is a typical Lithophaga and may be distin- 

 guished by its cylindric and elongate shape, with ventral and 

 dorsal sides nearly parallel. The posterior extremity is produced. 



Yorktown formation ; Yorktown, Va. 



