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1 42 I 



TERTIARY FAUNA OF FLORIDA 



severe scrutiny formerly given to such analogues. It becomes an interesting 

 question to decide whether this view is the correct one to take at the present 

 time. 



The average French V. planicosta is readih' separated from the average 

 Claiborne specimen by the greater breadth of the umbonal part of the valve 

 and the more rounded and convex dorsal slope, which carries with it a broader 

 area on the vertical faces of the nymphs. The anterior margin in front of the 

 lunule is also more prominent for a short distance. The other characters men- 

 tioned by M. Cossmann in his careful comparison are inconstant. 



Yet while these averages as above noted show a difference, there are occa- 

 sional American specimens which almost reproduce the French type, and the 

 first Claibornian specimen I happened to pick up for comparison with some 

 from Grignon fitted the opposite French valve almost exactly, except for a 

 quarter-inch space in front of the lunule. If the French specimens had been 

 collected in America no one would regard the differences as more than varietal. 

 The number of ribs is practically the same (thirty to thirty-five) in both, and 

 I can only lay to inaccurate counting the statements which allow twenty to 

 twenty-five ribs for either form. Both vary in having the ribs obsolescent 

 towards the base in the same way. A comparison of Figures i and 2 (densata) 

 given by M. Cossmann shows nearly as great a discrepancy between them as 

 between Figure i (planicosta) and Figure 2 (densata) in the matter of the 

 elevation of the beaks. 



There is, then, some excuse and, in fact, justification for the reference of 

 the American shell to the Lamarckian name. The estimation of values in such 

 cases is liable to a large personal equation, but it seems to me that historic and 

 stratigraphical paleontology will be benefited by regarding the diflrerences as 

 of subspecific rather than specific value. 



The references to the names which have been applied since that of Rogers 

 are as follows : 



Cardita densata Conrad, Proc. Acad. Nat. Sci. Phila., ii,, p. 173, 1844; Journ. Acad. Nat. 

 Sci. Phila., N. Ser. i., p. 130, pi. xiv., fig. 24, 1848; Venericardia d., Am. Journ. Conch., 

 i., p. 8, 1865. Lower Claiborne bluff. 



Venericardia planicosta var. regia Conrad, Am. Journ. Conch., i., p. 8, 1865 ; Venericardia 

 regia Conrad, Checkl. Eocene Fos. N. Am., p. 5, 1866. Eocene of Piscataway, Mary- 

 land. 



Cardita Hornii Gabb, Pal. Cal., i., p. 174, pi. xxiv., fig. 157, 1864; ii., p. 187, pi. xxx., fig. 

 830, 1868; Tejon Eocene of California. Venericardia Hornii Conrad, Checkl. Eocene 

 Fos. N. Am., p. 5, 1866. 



