682 SYSTEMATIC PALEOXTOLOGY 



Aphrodina tippana Conrad, 1868, Cook's Geol. of New Jersey, p. 727. 

 Aphrodina tippana Conrad, 1869, Am. Jour. Conch., vol. iv, p. 246, pi. xviii, 



fig. 5. 

 Aphrodina tippana Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 154, 



pi. xxii, figs. 6, 7. 



Aphrodina tippana Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 16. 

 Meretrix tippana Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv, p. 



607, pi. Ixviii, figs. 1, 2 (ex parte). 



Description. " Subtriangular, obsoletely striated concentrically ; ante- 

 rior sides slightly compressed, with an ascending basal margin, extremity 

 rather acutely rounded, distant from the apex ; base a little prominent in 

 the middle, subtruncated on either side; posterior end but slightly more 

 obtuse than the anterior; beaks prominent." Conrad, 1858. 



Type Locality. Owl Creek, Tippah County, Mississippi. 



Shell rather large and heavy, ovate-trigonal in outline, evenly but 

 strongly inflated ; lunule narrow, elongated, denned by an impressed line ; 

 area behind the umbones somewhat flattened but escutcheon not differenti- 

 ated ; umbones rather prominent by reason of their position at the apex of 

 an angle of a little more than 90 ; umbones evenly rounded but not 

 strongly inflated, the apices incurved, prosogyrate, slightly anterior in 

 position ; anterior extremity strongly arcuate, even a little nasute in front 

 of the lunule ; posterior dorsal margin obliquely arcuate, the lateral mar- 

 gin obscurely truncate ; ventral margin convex, more strongly upcurved in 

 front than behind ; external surface concentrically striated with a vigorous 

 incremental sculpture which becomes increasingly prominent toward the 

 ventral margin; ligament external, opisthodetic, mounted 011 rather a 

 slender nymph which extends a little less than half-way down the dorsal 

 margin ; cardinals three in number in each valve, the anterior cardinal of 

 the right valve short and slender, the middle cardinal trigonal, the poste- 

 rior laminar and elongated, anterior cardinal of the left valve trigonal and 

 stouter than that of the right, the middle cardinal rather short and slender, 

 the posterior elongated parallel to the nymph, a single short lateral elon- 

 gated parallel to the lunular margin in the right valve, received in a double 

 socket in the left; muscle impressions distinct but not conspicuous, the 

 anterior semi-elliptical, the posterior subcircular ; pallia! line distinct, the 



