MARYLAND GEOLOGICAL SURVEY 319 



seem more characteristic of Plum Point than of Cove Point, so tliat wliile 

 I am inclined to believe them to be from the latter place, the matter must 

 be left undecided until further search shall perhaps reveal other specimens 

 at one locality or the other. 



Length, 67 mm. ; height, 47 mm. ; diameter, 26 mm. 



Occurrence. — St. Mary's Formation. Cove Point (see above). 



Collection. — Johns Hopkins University. 



Superfamily CARDIACEA. 

 Family CARDIID/E. 



Genus CARDIUM Linne. 



Subgenus CERASTODERMA Morch. 



Cardium (Cerastoderma) i.aqueatum Conrad. 



Plate LXXXVI, Fig. 1. 



Cardium laqueatnm Conrad, 18-31, Jour. Acad. Nat. Sci. Phila., vol. vi, 1st ser., 



p. 258. 

 Cardium laqueatum Conrad, 1888, Fossils of the Medial Tertiary, p. 31, pi. xvii, 



fig- 1- 

 Cardium ingens Wagner, 1839, Dall, 1898, Trans. Wagner Free Inst. Sci., vol. v, 



p- 10, pi. iii, fig. 2. 

 Cardium {Cerastoderma) laqueatum Conrad, 18(53, Proc. Acad. Nat. Sci. Phila., vol. 



xiv, p- 576- 

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



Coll. (183), p. 9. 

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



pt. V, p. 1092. 



Description. — " Shell cordate, ventricose, thin, with about 33 subtri- 

 angular, transversely wrinkled ribs ; umbones prominent ; lunule not pro- 

 foundly impressed and somewhat lanceolate; cardinal tooth subulate." 

 Conrad, 1831. 



The ribs vary in number from thirty-three to thirty-six. The number 

 given in description published in 1838 (forty-three) is doubtless an error 

 in copying. Cardinal tooth prominent, lateral teeth distinct; anterior 

 and posterior muscle impressions and pallial line distinct; margin strongly 

 dentate in harmony with the ribbing; shell almost always broken and so 

 perfect specimens are rare. 



Length, 116 mm.; height, 97 mm.; diameter, 38 mm. 



