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72S 

 TERTIARY FAUNA OF FLORIDA 



Pecten Madisonius var. Sayanus n. var. 

 PLATE 26, FIGUKK 6. 



Upper Oligocene (Alum Bluff beds) of Oak Grove, Santa Rosa County, 

 Florida; on the Chattahoochee River at Old Chattahoochee Landing, at Rock 

 Bluff, and on the Chipola River in the Chipola beds. 



This form is the percursor in the Upper Oligocene of the typical Madl- 

 soiiins of the Miocene. It differs from the latter in its extreme compression, 

 the ribs, except in the umbonal region, being almost obsolete. Alt. 120, lat. 

 135, diam. about 16 mm. This is what has been referred to Jeffcrsoniits and 

 Madisonius by L. C. Johnson, Foerste, and other observers in the Floridian 

 Oligocene. 



The characteristics of /-*. Madisonius have been pointed out under P. 

 Jeffcrsotihts, from which it differs by its more compressed shell, more numerous 

 ribs, and coarser and more scabrous sculpture, as well as the deeper and wider 

 byssal notch. The young rarely have the scales continuous across the tops 



of the ribs. 



Pecten (Lyropecten) sp. indet. a. 



Lower Oligocene at Sulphur Springs ferry, Suwanee River, Suwanee 

 County, Florida (Vicksburg horizon ?). 



Shell small, thin, flattish, with eleven strong, rounded ribs, separated by 

 slightly wider interspaces ; submargins narrow, radially striated ; surface prob- 

 ably with concentric elevated and faint radial sculpture when perfect. Alt. 

 30, lat. 37, diam. about 7 mm. 



I have noted this species, as nothing like it has been described from the 

 Vicksburgian, and it has every appearance of being a precursor of the Miocene 

 Lyropectens. The fossil is a silicified pseudomorph, with the surface worn 

 and the ears defective. It is possible that the bed from which it came is the 

 upper Ocala or Nummulitic part of the Vicksburgian, though the rock shows 

 no Nummulites. 



Several closely allied species on the border line between the sections, and 

 which, except for their more delicate shells and smaller size, might equally 

 well be placed with the Lyropectens, will be found under the head of Nodi- 

 pcctcn, Ctdamys, and Placopccten. 



Pecten (Placopecten) Clintonius Say. 



/!,/,// Cliiitimitts Say, Journ. Arad. Nat. Sri. 1'liila., 1st Sen, iv., p. 135, pi. ix., tl^. 2, 1824. 

 /',;/,// i)hi^,-ll,ini,iis Conrad, Journ. Acrid. Nat. Sci. Fhila., ist Sur., vii., p. 153; not of 

 (iinclin, 1792. 



