FREE INSTITUTE OF SCIENCE 



1315 



TERTIARY FAUNA OF FLORIDA 



centric sulci across the middle part of the disk, the flat and polished interspaces 

 still showing traces of brown painting like notata. In a specimen 90 mm. long, 

 the vertical from the beaks falls only 7 mm. behind the front edge of the 

 valves ; in another from the same locality 80 mm. long, the same vertical is 

 20 mm. behind the front edge. In a specimen of the common or typical form 

 80 mm. long, the vertical falls at about 15 mm. 



In specimens from the Pleistocene of Sankoty Head, Nantucket Island, 

 Massachusetts, we find every gradation of concentric sculpture, from those 

 with the normal medial smooth area to others with close, fine, sharp, con- 

 centric lamellae entirely covering the shell, forming Verrill's variety antiqua, 

 which, so far as I have observed, is never paralleled among the recent shells. 



These differences result in very different-looking shells, and it would be 

 easy to select a considerable number of individuals with characters which, if 

 constant, would be regarded as specific ; consequently it is not unreasonable 

 to view with a lenient eye the work of Conrad and others based on a few 

 specimens, by which the specific names have been unduly multiplied. 



Venus campechiensis Gmelin. 

 Venus campechiensis Gmelin, Syst. Nat., v., p. 3287, 1792 (after Lister, Hist. Conch., pi. 



cclxxxiii., fig. 121, 1692) ; not of Dillwyn, Descr. Cat. Rec. Shells, i., p. 189, 1817. 

 Venus prceparca Say, Journ. Acad. Nat. Sci. Phila., ii., p. 271, 1822; Binney's Say, p. 95, 



vQxfl 



1050. 



Venus prceopaca De Kay, Zool. N. Y., v., p. 219, 1843, ex parte. 



Venus prceparea Sowerby, Thes. Conch., ii., p. 733, pi. clxi., fig. 200, 1853. 



Venus Mortoni Conrad, Journ. Acad. Nat. Sci. Phila., vii., p. 251, 1837; De Kay, Zool. N. 



Y., v., p. 219, 1843; Conrad, Am. Journ. Sci., 2d Sen, ii., p. 42, 1846; Reeve, Conch. 



Icon., xiv., Mon. Venus, pi. iii., fig. 7, 1864 (in errata). 

 Mercenaria Mortoni Deshayes, Cat. Conch. Brit. Mus., p. 114, 1853; Conrad, Proc. Acad. 



Nat. Sci. Phila., vii., p. 29, 1854 ; H. and A. Adams, Gen. Rec. Moll., ii., p. 4*9, 1857 ; 



Holmes, Post-Pi. Fos. S. Car., p. 34, pi. vi., fig. 12. 1858; Tryon, Am. Mar. Conch., 



p. 138, figs. 391-2, 1874. 

 Mercenaria prceparca Deshayes, Cat. Conch. Brit. Mus., p. 115, 1853; H. and A. Adams, 



Gen. Rec. Moll., ii., p. 419, 1857. 

 Venus calcarea Philippi, Abbild. u. Beschr. Conch., i., p. 175, Venus, pi. iii., fig. i, 1844 



(young shell). 



Chione calcarea Deshayes, Cat. Conch. Brit. Mus., p. 123, 1853. 

 Venus tenuilamellata Sowerby, Thes. Conch., ii., p. 733, pi- clxi., fig. 195, 1853 (young 



shell). 

 Venus alboradiata Sowerby, Thes. Conch., ii., p. 732, pi. clxi., fig. 199, 1853 ; Reeve, Conch. 



Icon., xiv., Mon. Venus, pi. iii., fig. 7- 



