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7^7 

 TERTIARY FAUNA OF FLORIDA '**' 



rccten Johnsoni Clark (Bull. U. S. Geol. Surv., No. 141, p. 85, fig. 3 a, 3 /;, 

 1896), from the Eocene of Maryland, is a young shell, not fully exhibiting the 

 adult characters, and of which the type specimen seems worn. It belongs in this 

 vicinity, but has twenty ribs, with single short intercalary threads, crossed only 

 by fine lines of growth. The specimens were obtained from Potomac Creek, Va. 



Pecten (wahtubbeanus var. ?) Willcoxii n. s. 

 PLATE 29, FIGURE 4. 



Eocene of Clarke County, Mississippi, and of the Wahttibbee hills 

 (Claibornian) ; Johnson and Burns. 



Shell small, broad, flattish, thin ; left valve with about sixteen narrow, 

 rounded, elevated ribs, with somewhat sparse, regularly spaced prickles on 

 their tops ; between the ribs are similar, but lower and smaller, non-dichoto- 

 mous radial threads; submargins very narrow, nearly plain, with faint Cainp- 

 tonectcs striation ; ears small, subequal, except the byssal ear, which is longer, 

 narrow, with a deep sinus and conspicuous fascicle, and about six scabrous 

 radii, the right posterior ear with concentric striae and only faint traces of a 

 few radii ; the cars on the left valve similar, with five or six strong scabrous 

 threads ; internal basal margin of left valve with short flutings in harmony 

 with the radial sculpture ; the disk not grooved ; in the right valve the internal 

 channels are more pronounced ; the right hinge-line has a single crural ridge 

 parallel with the margin on each side of the pit. Alt. 23, lat. 24 mm. 



This form is closely related to P. wahtubbeanus, from which it differs by 

 the isolated character of the prickles on the ribs, which are replaced in ivah- 

 tubbeaiins by more or less continuous concentric lamellation, while the ribs 

 of the right valve of the latter are more or less split up, but in P. Willcoxii 

 present the appearance of a fascicle of separate threads. In worn specimens 

 of wahtubbeanus the ribs appear rounded and plain after the removal of the 

 scales ; in Willcoxii the division into threads is distinct. Nevertheless it is 

 possible that a larger series may show the two forms to be merely the ex- 

 tremes of a single species. From P. tnembranosiis the present form is easily 

 distinguished by wider hinge-line, larger ears, thinner shell, and by its radial 

 threads fasciculated rather than subequally level. It is named in honor of 

 Mr. Joseph Willcox, to whom our Tertiary Paleontology is so much indebted. 



Pecten (Chlamys) Deshayesii I.ca. 



l',i I, n n,-sliity<-sii l.c;i, Ccinlr. (Ii-ol., p. 87, pi. 3, li^. C>6. 1833. 

 1',',/,-n I.y,-lli I.ea, />. <//., p. 88, pi. 3, fig. 67. (Young.) 



