400 SYSTEMATIC PALEOXTOLOGY 



eons impressed ; striated, the margins not pouting in the middle ; beaks 

 prominent, obtuse ; interior lirilliantly pearl}^, muscular impressions deep ; 

 the basal margins tinely crenulate; hinge strong, wide; the chondrophore 

 oblique, heavy; anterior teeth wide, strong, about seventeen, posterior 

 about seven. . . . 



" This species difEers from the preceding [N. chipolana] by its more 

 trigonal, heavy, and pearly shell, its wider and proportionately heavier 

 hinge, and its impressed instead of merely flattened escutcheon. The 

 Maryland specimens are usually larger and more worn than the types 

 from West Florida; both retain a purplish tint in their nacre." Dall, 

 1898. 



Length, 4.75 mm.; height, 4 mm.; diameter, 2.5 mm. (Dall). 



Occurrence. — St. Mary^s Formation. Cove Point, Langiey's Bluff, 

 St. Mary's River. Choptank Formation. Jones Wharf. 



Collections. — Maryland Geological Survey, Johns Hopkins University, 

 U. S. National Museum. 



Nucula taphria Dall. 

 riate CVIII, Figs. 9, 10, 11. 



Nucula tdphria Dall, 1898, Trans. Wagner Free Inst. Sci., vol. ill, pt. iv, p. 576, 

 pi. xxxii, tig. 14. 



Description. — " Shell small, very solid, rounded cuneiform, with few 

 strong, distant concentric grooves, like marks of resting stages, which 

 extend clear over the shell, otherwise smooth; beaks prominent, turgid; 

 lunule absent ; escutcheon faintly indicated ; ])Osterior end sulitruncate, 

 anterior produced and rounded, base moderately arcuate ; interior hardly 

 nacreous, muscular impressions large and distinct ; basal margins entire ; 

 hinge strong and heavy; chondrophore wide, distinct, a little oblique; 

 anterior teeth thirteen, posterior six or seven. . . . 



" This interesting species is related to the recent iV. delpMnodonta 

 Mighels, which is a more rounded and less oblique shell, without the 

 strong concentric grooves of N. taphria." Dall, 1898. 



Length, 2.9 mm.; height, 2.25 mm.; diameter, 1.5 mm. (Dall). 



Occwrence. — St. Mary's Formation. St. Mary's River. Choptank 

 Formation. Jones Wliarf. 



Collections. — Maryland Geological Survey, Johns Hopkins University, 

 U. S. National Museum. 



