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TERTIARY FAUNA OF FLORIDA 



posterior left cardinal not so disproportionately long, slender ; the posterior 

 right cardinal grooved ; margins entire ; the pallial sinus nearly obsolete. 



This is Mercenaria Cossmann, 1886, not of Schumacher, 181 7. The coarse 

 hinge-rugosities and crenulated margin of the true Mercenaria have no parallel 

 here. The species which are included in Cossmann's list and have a deep 

 though small sinus might be referred to the preceding section, from which they 

 hardly differ. 



Section Textivenus Cossmann. Type Venus texta Lamarck. Parisian 

 Eocene. 



Shell ovate, moderately convex, the surface sculptured by fine, obliquely 

 reticulate or divaricate, subequal, thread-like ridges ; lunule small, circum- 

 scribed ; escutcheon bordered by a radial ridge ; internal margins smooth, the 

 right posterior dorsal margin behind the hinge-plate grooved to receive the 

 bevelled edge of the opposite valve ; teeth normal, the posterior right cardinal 

 broadly bifid ; pallial sinus small, angular, free. 



Section Samarangia Dall, 1902. Type Venus quadrangularis Adams 

 and Reeve. 



Shell rounded quadrate, subcompressed, with an impressed lunule ; sculp- 

 ture of concentric striation more forcible distally ; hinge solid, normal, the two 

 right posterior cardinals bifid ; the pallial sinus small, the inner margins of 

 the valves smooth. 



This type includes Venus lenticularis Sowerby, and the shell is massive and 

 solid. 



The only representatives of Marcia in the North American Tertiary are M. 

 subdiaphana Carpenter, described as a dementia, and which, according to 

 Cooper, occurs in the Pliocene of San Diego, California, and the Pleistocene 

 of the California coast at several localities. The Tapes gibbosus of Gabb has 

 a very similar appearance externally, and may probably also be referable to 

 Marcia. It is found in the Miocene of Coos Bay, Oregon, horizon of the Em- 

 pire beds, and also in the Miocene of Mendocino County, California. 



Genus PAPHIA Bolten. 

 <^Paphia Bolten, Mus. Boltenianum, p. 175, 1798, ed. ii., p. 122, 18:9; not Paphia Lamarck, 



1799 and 1801, or Fabricius, 1808, or Oken, 1815. 

 Tapes Megerle v. Miihlfeld, Entw. neuen Syst. der Schalth. in Mag. Ges. Naturf. Freunde, 



p. Sl> 181 1 {Venus literata L.)- 

 Venerupis (sp.) Lamarck, An. s. Vert, v., pp. 506-7, 1818. 



