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TERTIARY FAUNA OF FLORIDA 



London, vi., p. 52, 1850) not being figured, the number of ribs and the pro- 

 portional measurements being omitted from Sowerby's diagnosis, can hardly 

 be identified, though it probably resembles this species, which has about thirty 

 rounded ribs with subequal channelled interspaces, the anterior ribs being 

 granulosa or nodiferous, the shell remarkably high, short, solid, and wide. 

 The measurements of a well-grown specimen are: alt. 42, Ion. 45, and diam. 

 44 mm.; the length of the cardinal area is 28 mm. It is one of the species 

 on the border line between Scapliarca and Aiiadara, the two valves being 

 similarly sculptured and almost equal. 



Scapharca (Scapharca) Lesueuri Dall. 

 Lesueur, Walnut Hills Fos., pi. v., fig. 8, 1829. 

 Area mississippiensis Conrad, Journ. Acad. Nat. Sci. Phila,, 2d Ser., i., p. 125, pi. 13, 



figs. II, 15 ; Proc. Acad. Nat. Sci. Phila., iii., p. 294, 1848. Not 

 Byssoarca mississippiensis Conrad, Journ. Acad. 1. c, p. 125, pi. i, fig. 323. 

 Anomaloca7-dia mississippiensis Conxz.di., hxa.]o\.\x'a. Cavi<i\\.,\., ^. 11, 1865. Not 

 Cuciillaarca mississippiensis Conrad, Am. Journ. Conch., i., p. 11, 1865. 



Vicksburgian Oligocene of Mississippi. 



It is obvious that the same specific name cannot be used twice in the 

 same genus for a valid species, and so I have proposed to call the present one 

 Area Lesueuri, in honor of the excellent naturalist who was the first to call 



attention to it. 



Scapharca (Scapharca) arata Say. 

 Area arata Say, Journ. Acad. Nat. Sci. Phila., 1st Ser., iv., p. 137, pi. 10, fig. i, 1824; 



Conrad, Fos. Med. Tert., No. 3, p. 58, pi. 30, fig. 6, 1845. 



Miocene of St. Mary's County, Maryland ; Burns. 



This species is the oldest of the group to which it belongs, which 

 includes A. improcera, A. htecula, A. plicaiura, etc., and which is represented 

 in the recent fauna by A. transversa Say. 



Scapharca (Scapharca) improcera Conrad. 

 Area improcera Conrad, Fos. Med. Tert., p. 60, pi. 31, fig. 5, 1845. 

 Scapharca improcera Conrad, Proc. Acad. Nat. Sci. Phila. for 1862, p. 579, 1863. 

 Area plicaticra (juvenis) Heilprin, Proc. Acad. Nat. Sci. Phila. for 1881, p. 451. 



Upper Miocene of Warwick, Virginia; of Duplin County and Wil- 

 mington, North Carolina; of Timminsville and Darlington, South Carolina, 

 Burns ; Pliocene of the Caloosahatchie River and Shell Creek, Florida, Dall 

 and Willcox. 



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