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Son 

 TERTIARY FAUNA OF FLORIDA -"^ 



This fine Spisula is sharply distinguished from any other American 

 species by its high and triangular form, short, excavated hinge-plate, and the 

 inequilaterality of the shell. 



Spisula (Hemimactra ?) magnoliana n. s. 

 Plate 27, Figure 29. 



Chesapeake Miocene of Magnolia, Duplin County, North Carolina; 

 Burns. 



Shell small, equilateral, somewhat compressed, with small, little-elevated, 

 pointed, adjacent beaks; surface smooth except for lines of growth and a 

 feeble angulation extending backward from the umbo to the lower posterior 

 margin; ends nearly equally rounded, the posterior slightly more pointed, 

 the base moderately and evenly curved; pallial sinus small, angular, very 

 short; hinge normal, feeble, with short granulose laterals. Lon. 17, alt. 10, 

 diam. 7 mm. 



A single left valve was obtained by Burns, which much resembles a Mii- 

 linia except in the character of the ligamentary attachment. It differs from 

 the other species of the formation by its rounded ends and subcylindric form. 



Spisula (Heroiniactra) subponderosa Orbigny. 

 Plate 27, Figures 3, 16. 

 Mac/ra poiidcrosa Conr., Journ. Acad. Nat. Sci. Phila., vi., p. 228, 1830 ; Medial Teit., 

 p. 25, pi. 14, fig. I, 1838 ; not of Eichwald, Nat. Skizze von Lith., p. 207, 1830, 

 nor of Philippi. 

 Macira subponderosa Oi'b., Prodr. Pal., iii., p. 100. 

 Mactrodesma ponderosa Conr., Am. Journ. Conch., iv., p. 247, 1S69. 

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

 This fine shell differs from the typical Mactromeris of Conrad only in its 

 shorter and more inflated shell and thicker valves, features which can hardly 

 be claimed to have more than a specific value. If 5. mmjlandica. had a thick 

 shell it would closely resemble the present species. But MacU'omcris differs 

 only from Hcvihiiactra in having the laterals smooth or granular without cross- 

 striation, and very little study will convince anyone that this character has 

 very slight systematic value. Conrad's name having been used previously by 

 Eichwald, Orbigny substituted for it in the same year the term subponderosa, 

 which should be adopted under the rule that such rectifications are not to be 

 disturbed by subsequent generic references of the species to which they refer. 



