370 SYSTEMATIC PALEONTOLOGY 



Description. — Shell irregularly rounded; upper valve irregularly and 

 moderately convex, beak but slightly prominent and very near the mar- 

 gin, the external surface ornamented near the beak with fine, radiating, 

 undulated lines of minute scales which become rounded pustules nearer 

 the margins ; within almost smooth : lower valve flat, smooth except for 

 slight, irregular, concentric growth lines. 



The shape varies according to the position occupied during growth 

 but is usually irregular. A magnificent specimen of an upper valve 

 from Plum Point, with beak broken, is very thick, symmetrical and pro- 

 foundly and regularly elevated, being in height 45, width 46, and diam- 

 eter 13 mm. At several localities young specimens have been found that 

 in some cases show the ornamentation of A. aculeata and have been re- 

 ferred to it, while in others no ornamentation has developed and they are 

 considered as indeterminate, though most probably they are also the 

 young of A. aculeata. 



Height, usually about 37 mm.; width, 35 mm., but see preceding 

 description. 



Occurrence. — St. Mary's Formation. St. Mary's Eiver, Cove 

 Point ( ?) . Choptank Formation. Jones Wharf, Trappe Landing ( ?) . 

 Calvert Formation. Plum Point, 3 miles south of Chesapeake 

 Beach (?). 



Collections. — Maryland Geological Survey, Johns Hopkins University, 

 U. S. National Museum. 



Superfamily PECTINACEA. 



Family LIMID/E. 



Genus LIMA (Bruguiere) Cuvier. 



Lima papyria Conrad. 

 Plate XCVIII, Fig. 6. 



Lima papyria Conrad, 1841, Proc. Acad. Nat. Sci. Phila., vol. i, p. 30. 

 Lima papyria Conrad, 1845, Fossils of the Medial Tertiary, p. 76, pi. xliii, fig. 7. 

 Lima papyria Conrad, 1863, Proc. Acad. Nat. Sci. Phila., vol. xiv, p. 582. 

 Lima papyria Meek, 1864, Miocene Check List, Smith. Misc. Coll. (183), p. 4. 



