TRANSACTIONS OF WAGNER 

 722 



TERTIARY FAUNA OF FLORIDA 



for a recent species from the Mediterranean by Risso, so I have substituted 

 another. 



Pecten (Lyropecten) Jeffersonius Say. 

 Pectcn Jcffersonitts Say, Journ. Acad. Nat. Sci. Phila., ist Ser., iv., p. 133, pi. 9, fig. i, 



1824 ; Conrad, Fos. Medial Tert., p. 46, pi. 22, fig. i, 1840. 



iVIiocene of the Nansemond, James, and York Rivers, Virginia, at Suffolk, 

 City Point, Coggins Point, Bellefield, and Grove Wharf; also in the Miocene 

 of North Carolina. 



Pecten Jeffersonius var. edgecombensis Conrad. 

 Pecten edgecombensis Conrad, Proc. Acad. Nat. Sci. Phila. for 1862, pp. 291, 581, 1863. 

 Liropccien carolineiisis Conrad, in Kerr, Geol. N. Car., App., p. 18, 1875 (from type). 



Miocene of Coggins Point, Petersburg, Grove Wharf and Gaskins 

 Wharf, York River, and Suffolk, Virginia; Langley's Bluff, Maryland, and 

 near Tarboro', Edgecombe County, North Carolina. 



Pecten Jeffersonius var. septenarius Say. 

 Pecten septe?iari!ts Say, Journ. Acad. Nat. Sci. Phila., ist Sen, iv., p. 136, pi. ix., fig. 3, 



1824. 

 Pecten septemnarins Conrad, Med. Tert., p. 47, pi. 22, fig. 2, 1840. 



Miocene of St. Mary's River, Maryland; Petersburg, Virginia; Duplin 

 County, North Carolina, and the Peedee River, South Carolina. Rather rare. 



It is probable that no group of Pectens shows more interestingly the 

 factors of variation in sculpture than that comprising the east American Lyro- 

 pectens. 



These shells (L. Jeffersonius and Madisoniiis) illustrate the different muta- 

 tions in the most instructive way. They are ribbed shells, nearly equilateral 

 and equivalve, with a surface sculpture of fine radial scabrous threads. It is 

 probable — since the range of Jeffersonius is more restricted and its earliest 

 appearance in the Miocene, while Madisoniiis is represented by precursors in 

 the Oligocene — that Jeffersonius is an offshoot from Madisonius and that P. 

 Clintonius, even, may be another. To determine the range of variation in the 

 matter of the primary ribs, I have counted them on all the specimens in the 

 collection, nearly one hundred, with the following result: 



A. Variety septenarius. Three with seven, eleven with eight ribs. 



B. Y7i.Yie\.y Jeffersonius s.s. Eighteen with nine, twenty-eight with ten, thirteen 



with eleven ribs. 



