320 SYSTEMATIC PALEONTOLOGY 



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

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

 south of Governor Eun, Flag Pond, Jones Wharf, Turner, Pawpaw Point, 

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



Collections. — Maryland Geological Survey, Johns Hopkins University. 



Cardium (Cerastoderma) leptopleurum Conrad. 

 Plate LXXXVI, Fig. 2. 



Ganliin/i leptopleura Conrad, 1841, Proc. Acad. Nat. Sci. Fbila., vol. i, p. 29. 

 Cardium leptopleura Conrad, 1842, Jour. Acad. Nat. Sci. Pbila., voL viii, 1st ser., 



p. 184. 

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



fig. 5. 

 Cardium {Cerastoderma) leptopleura 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, 1095. 



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, 1841. 



Eibs 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 craticuloides Conrad, 1845, Fossils of the Medial Tertiary, p. 66, pi. xxxvii, 



fig. 3. 

 Cardium (Cerastoderma) craticuloides Conrad, 1863, Proc. Acad. Nat. Sci. Phila., 



vol. xiv, p. 576. 

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



Coll. (183), p. 8. 

 Cardium (Cerastoderma) craticuloides Whitfield, 1894, Mon. xxiv, U. S. Geol. Survey, 



p. 66, pi. X, figs. 16-19. 



