320 SYSTEMATIC PALEONTOLOGY 



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

 St. Mary's Eiver. Choptank Formation. Governor Eun, 2 miles 

 south of Governor Run, Flag Pond. Jones Wharf, Turner, Pawpaw Point, 

 Cuckold Creek, St. Leonard Cjeek, Dover Bridge, Greensboro, Sand Hill. 



Collections. — Maryland Geological Survey, Johns Hopkins University. 



Cardium (Cerastodeema) leptopleurum Conrad. 

 Plate LXXXVI, Fig. 2. 



Cardintii leptopUimt Conrad, 1841, Proc. Acad. Nat. Sci. Phila., vol. i, p. 29. 

 Cardimn leptopleura Conrad, 1842, Jour. Acad. Nat. Sci. Phila., vol. viii, 1st ser., 



p. 184. 

 Cardium leplopleura Conrad, 1845, Fossils of the Medial Tertiary, p. 66, pi. xxxvii, 



fig. 5. 

 Cardium (Cerastodermu) hptoplenra Conrad, 1863, Proc. Acad. Nat. Sci. Phila., vol. 



xiv, p. .576. 

 Cardium (Cerastoderma) leptopleura Meek, 1864, Miocene Check List, Smith. Misc. 



Coll. (183), p. 9. 

 Cardium (Cerastoderma) leptopleura Dall, 1900, Trans. Wagner Free Inst. Sci., vol. 



iii, pt. V, 109.5. 



Description. — " Subtrigonal, ventricose; ribs about 31, prominent, dis- 

 tant, angular, carinated; umbo prominent, oblique; lateral teeth very 

 prominent; inner margin widely and deeply crenate." Conrad, IS-il. 



Ribs vary in number from twenty-eight to thirty-one; in transverse 

 section, profile of each rib rounded and as broad across the base as tall, 

 becoming in older specimens even broader and more flatly rounded or 

 even flat ; distance from beak to base rather short as compared with length 

 of shell ; hinge line proportionally long. 



Length, 48 mm. ; height, 47 mm. ; diameter, 17 mm. 



Occurrence. — Calvert Formation. Plum Point, near Jewell (rare). 



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



Cardium (Cerastoderma) craticuloide Conrad. 

 Plate LXXXVI, Fig. 3. 



Cardium craticulokles Conrad, 1845, Fossils of the Medial Tertiary, p. 66, pi. xxxvii, 



fig. S. 

 Cardium [Cerastnderiua) cratieuloides Conrad, 1863, Proc. Acad. Nat. Sci. Phila., 



vol. xiv, p. 576. 

 Cardium (Cerastoderma) craticuloidcx Meek, 1864, Miocene Check List, Smith. Misc. 



Coll. (183), p. 8. 

 Cardium (Cerastoderma) cratlciiloides Whitfield, 1894, Men. xxiv, IT. S. Geol. Survey, 



p. 66, pi. X, figs. 10-19. 



