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TERTIARY FAUNA OF FLORIDA ' "^ 



In addition to the major and minor byssal scars on the disk, there is a 

 small semilunar scar near the resiliary pit, due to a branch of the byssal 

 muscular system. The " Placiiiia papyracea" of which the nepionic foramen 

 is figured by Fischer (Man. Conch., p. 953, fig. 701), belongs to the genus 

 Ephipphun. The dynamic relation between the size and position of the byssal 

 foramen and the byssal scars is sufficiently obvious. The only American 

 fossil referred to Plaauia, — P. scabra Morton, — as already indicated, belongs 

 to the Cretaceous, and is placed by Conrad in his genus Paranoviia. 



Genus CAROLIA Cantraine. 

 Carolia Cantraine, Bull. Acad. Sci. Brux., 1S38, p. iii. Type C. placu9ioides C3Lr)Xrs.n\e ; 



Fischer, J. de Conchyl., xxviii., p. 345, pi. xii., 1880 ; Man., p. 932, fig. 700, pi. xvi., 



fig. 7, 1 886. Lower Eocene of Egypt. 

 Hemiplaatna (Sby. MS.) Gray, P. Z. S., 1849, p. 123. Type H. Rosieri Sby. Cf. 



Roziere in Descr. de I'Egypte, Mineralogie, pi. xi., fig. 6. 



Shell thin, nacreous, with radiating striae, the right valve flattened; resilium 

 rounded-triangular, internal, large, attached in the right valve to a pedunculate 

 chondrophore seated on the anal side of the umbo and extended adorally so 

 as to bring the middle of the resilium in the median line of the valve; in the 

 left valve the resilium is attached in the cavity of the umbo, leaving a broad, 

 fan-shaped, thickened scar of attachment, of which the anterior and posterior 

 margins are elevated into diverging lainellae. In the young stage the right 

 valve is perforate for the passage of a byssus or byssal plug, which gradually 

 atrophies, so that in the full-grown shell the sinus and perforation are closed 

 with shelly matter and so overshadowed by the heavy chondrophore as to be 

 hardly perceptible even as a scar. It should be observed that the attachment 

 of the resilium is wholly posterior, and not the result of the merging of an 

 anterior and posterior chondrophore. The scar of the adductor in each valve 

 is single, orbicular, and nearly central, with two very minute accessory pedal 

 or byssal muscular scars above it in the left valve. 



This genus has been discussed by Gray and Fischer, the latter giving 

 some instructive figures of the gradual obliteration of the sinus and of the 

 analogous early sinus in EpJiippiuin papyracciim. 



For a fine specimen of the Carolia figured by Roziere in Savigny's 

 Egypte I am indebted to Lieutenant S. M. Ackley, U. S. N., who obtained it 

 from the Eocene Tertiary bed underlying the desert, about five miles west 

 from the bed of the ancient Lake Mceris, in the Fayoum. It measures thir- 



