MARYLAKD GEOLOGICAL SURVEY 331 



coelous; anterior dorsal margin direct, declining; posterior dorsal margin 

 strongly arched or rounded; anterior side rounded cuneate; posterior 

 side longer, more inflated and ovate; posterior end slightly truncate; 

 teeth prominent; muscle impressions and pallial line distinct; interior 

 radial striae distinct, especially near basal margin; exterior polished; 

 basal margin direct. 



Length, 8 mm.; height, 7 mm.; diameter, 1.7 mm. 



Occurrence. — Choptank Formation. Greensboro. Calvert For- 

 mation. Plum Point (U. S. National Museum). 



Collections. — Maryland Geological Survey, U. S. National Museum. 



BORNIA DEPRESS A n. Sp. 



Plate LXXXVIII, Fig. 11. 



Description. — Shell rounded ovate; anterior side slightly produced; 

 anterior end somewhat more sharply rounded than posterior end; base 

 very gently curved; beak not prominent, rising very little above profile 

 of dorsal margin; shell thin and only moderately convex; outer surface 

 smooth, inner surface with very distinct muscle impressions and pallial 

 line; teeth prominent, anterior one set almost transverse to hinge line, 

 posterior one more declining. 



Length, 4.6 mm.; height, 3.2 mm.; diameter, 0.9 mm. 



Occurrence. — Calvert Formation. Plum Point. 



Collection. — U. S. National Museum. 



Genus KELLIA Turton. 



Kellia rotundula n. sp. 



Plate LXXXVIII, Figs. 12, 13. 



? Kellia sp. indet. Dall, 1900, Trans. Wagner Free Inst. Sci., vol. iii, pt. v, p. 1154. 



Description. — Shell delicate, rounded, elliptical; highly inflated; beak 

 almost medial, not prominent; posterior end slightly truncated squarely; 

 hinge area prominent; teeth distinct, moderately stout; muscle impres- 

 sions and pallial line faint; faint interior radial markings visible; ex- 

 terior polished, smooth. 



Length, 7 mm.; height, 6 mm.; diameter, 1.4 mm. 



