TRANSACTIONS OF WAGNER 

 1418 



TERTIARY FAUNA OF FLORIDA 



Venericardia planicosta Lamarck. 



Venericardia planicosta Lamarck, Syst. des An. s. Vert, p. 123, 1801 ; G. Fischer, Mus. 

 Demidoff, iii., p. 260, 1807; Lamarck, Ann. du Museum, vii., p. 55, ix., pi. xxxi., fig. 

 10 ; Sowerby, Min. Conch., i., pi. 1., 1814; Lamarck, An. s. Vert., v., p. 669, 1818; 

 Deshayes, Coq. Fos. des envir. de Paris, i., p. 142, pi. xxiv., figs. 1-3, 1824; Def ranee, 

 Diet. Sci. Nat., Ivii., p. 231, 1828; Bronn, Leth. geogn., ii., p. 946, pi. xxxviii., fig. 7, 

 1836; Cossmann, Cat. Illustre, ii., p. 90, 1887; Bull. Soc. Geol. de France, 4me Ser., 

 i., p. 653, 1901. 



Cardita planicosta Deshayes, Enc. Meth., Vers., ii., p. 198, 1830; Traite elem. Conch., i., 

 pi. xxxii., figs. 1-3, 1842; Bronn, Index Pal., i., p. 227, 1848; Orbigny, Prodr. Pal., 

 ii., p. 324, 1850; Morris, Cat. Brit. Fos., 2d ed., p. 191, 1854; Deshayes, An. s. Vert, 

 bas. Paris., i., p. 756, 1858. 



Eocene of northern France, of Belgium and England, but not of southern 

 Europe. 



In taking up the great Venericardias of this type belonging to our Tertiary 

 it is convenient also to consider this extreme, eastern offshoot of the original 

 American stock, to many of the forms of which Lamarck's name has loosely 

 been applied. 



When Lamarck described the genus he cited two species, V. imbricata and 

 the present one, without selecting a type. Blainville some years later named 

 V. planicosta as an example of the genus, and it has been generally accepted 

 as the type. It is, however, undeniable that the two species of Lamarck stand 

 for two groups which are represented side by side in all the Eocene horizons 

 and still have representatives in the recent fauna, though that represented by 

 V. planicosta seems absent from the Oligocene, Miocene, and Pliocene of North 

 America. Its recent analogue occurs only on the Pacific coast in tropical 

 waters. The distinctions are chiefly those of form, the imbricata type being 

 rounded rhomboidal and the planicosta type arcuate triangular. These dis- 

 tinctions seem hardly of sectional value, yet they have persisted since the Meso- 

 zoic and represent, as it were, in each case a niche in the fauna which each 

 respectively is best adapted to fill. The name Megacardita Sacco, given to a 

 rhomboid form which differs from the imbricata type only by the greater 

 smoothness of its ribs (a specific character only), is available if anyone wishes 

 to designate these differences by a distinctive name. 



Owing to their abundance in varieties, individuals, and their wide distribu- 

 tion in America, the distribution of the fossil planicosta on those coasts towards 

 which migration might be favored by ocean currents and not in the Medi- 

 terranean region, and the presence in American waters of the only living repre- 



