MARYLAND GEOLOGICAL SUEVEY 397 



Length, 11.5 mm.; height, 6 mm.; diameter, 2.3 mm. 

 Occurrence. — Calvert Formation. Plmn Point. 

 Collections. — Maryland Geological Survey, Johns Hopkins University, 

 U. S. National Museum. 



Leda concentric a (Say). 

 Plate CViri, Figs. 1, 2. 



Nucula co/icentrica Say, 1834, Jour. Acad. Nat. Phila., vol. iv, 1st sen, p. 141. 

 Nucula concentrica Say, 18S1, Amer. Concli., pi. xii. 



NucuJa concentrica Conrad, 184.5, Fossils of the Medial Tertiary, p. 57, pi. xxx, tiof. 3. 

 Nucula eborea Conrad, 1846, Proc. Acad. Nat. Sci. Phila., vol. iii, p. 24, pi. i, fig. 4. 

 Not Yoklia eborea Conrad, 1860, Jour. Acad. Nat. Sci. Phila., 2nd ser., vol. iv, 



p. 29.5, pi. xlvii, flg. 26; nor Conrad, 1863, Proc. Acad. Nat. Sci. Phila., vol. 



xiv, p. .581; nor Meek, 1864, Miocene Check List, Smith. Misc. Coll. (183), p. 5. 

 Nucula concentrica Conrad, 1863, Proc. Acad. Nat. Sci. Phila., vol. xiv, p. 581. 

 Nucula concentrica Meek, 1864, Miocene Check List, Smith. Misc. Coll. (183), p. 5. 

 Leda concentrica Dall, 1898, Trans. Wagner Free Inst. Sci., vol. iii, pt. iv, p. 588. 



Description. — " Transversely elongate-subovate, rostrated, concentri- 

 cally striated. 



" Shell convex; rostrum considerably narrowed towards the tip : surface 

 concentrically striated with numerous, regular, equidistant, rounded 

 lines: beaks rather behind the middle: ligament margin a little concave: 

 series of teeth angulated at the beaks. . . . 



" The regularly striated surface gives this shell a very pretty appear- 

 ance. In outline it has some resemblance to the rostrata." Say, 1824. 



Length, 6 mm.; height, 4 mm.; diameter, 1.1 mm. 



Occurrence. — St. Mary's Formation. St. Mary's County (Say) ; 

 Pocomoke City at a depth of 53 to 75 feet in a well boring where it may 

 be later than Miocene. 



Collections. — Maryland Geological Survey, Johns Hopkins University, 

 Wagner Free Institute of Science. 



Genus YOLDIA Mollev. 

 YoLDiA L.^vis (Say). 

 ♦ Plate CVIIT, Figs. 3, 4. 



Nucula lievis Say, 1824, Jour. Acad. Nat. Sci. Phila., vol. iv, 1st ser., p. 141, pi. x, 



tig. 5. 

 Nucula heiHs Say, 1831, Amer. Conch., pi. xii. 



