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719 



TERTIARY FAUNA OF FLORIDA 



This species when young is more ovate, when adult orbicular. The um- 

 bones are smooth, by which it may be instantly distinguished from P. {Amu- 

 sinin) Lyoiii. Whether it can be separated from Amusiiiiii Mortoiii Rav. or 

 not will depend upon comparisons for which the material at my command is 

 as yet insufficient. The species is still living in Antillean and Gulf waters. 

 Alt. 50, lat. 55 mm. 



Amusium Lyoni Gabb. 

 Plcicronectia Lyoni Gabb, Journ. Acad. Nat. Sci. Phila. , 2d Ser., viii., p. 347, pi. 45, fig. 



ila-b, 1 88 1. 

 Pcclen Mo?'t07n Cu^'gy , op. cit., p. 451, 1874. 



Oligocene of Anguilla, Guppy ; of Bowden, Jamaica, Guppy ; Pliocene 

 of Tehuantepec, Spencer; and of Costa Rica, Gabb. 



This form, otherwise very similar, is immediately distinguishable from P. 

 (A.) papyraccus by the nepionic sculpture of the umbonal region. 



Most of the recent PectinidcB of the Gulf and Antillean region are found 

 associated with other recent shells in the raised beaches and reefs so numer- 

 ous on the islands. It is not necessary to enumerate them here, but I may 

 mention that Pecten {Euvold) ziczac L. is quite abundant in the Pleistocene of 

 Barbados. 



FOSSIL PECTENS OF THE FLORIDIAN REGION. 

 The environs being now cleared, we may proceed to consider the species 

 represented in the Floridian horizons and the adjacent portions of the south- 

 eastern United States. 



Peoten (Pecten) Poulsoni Morton. 

 Pcctcii sp. Lesueur, Walnut Hills Fos., pi. 5, figs. 3, 4, 1829. 

 Pecten Pou/soni Morton, Syn. Org. Rem., p. 59, pi. xix., fig. 2, 1834. 

 Pecten elixatus Conrad, Proc. Acad. Nat. Sci., ii., p. 174, 1846. 

 Janira proniejis de Gregorio, Mon. Claib., p. 181, pi. 21, figs. 17-25, 1890. 



Oligocene (Vicksburgian) at Vicksburg, Carson's Creek, Wayne County, 

 and Shubuta, Mississippi ; near Rosefield, Louisiana, Vaughan ; near Archer, 

 Florida, Dall ; at Jarves Spring, Florida, Willcox. Abundant in the Vicks- 

 burgian beds generally, but hitherto frequently confused with P. pcrplamis 

 Morton. 



This is a very solid and characteristic little shell. The ribs in young 

 specimens are often simple ; in adults they are apt to take on two or three 

 longitudinal grooves. The crura are strong and well developed. 



