Snperfamily A IT I.! I ;. . .J A 

 Family ilnomiclae. 

 Genus PLACLTiJIOLTIA Broderip. 



PIAOUNiUTOMIA LITEOBLETA Dall . 



Pla.ounanomia lithobleta Dall, 18''8, Trpns. V/gn-ner Free Inst. Sci., 

 Philadflphia, vol. ?, pt. 4, vo, 778-779. 



-QesGrlptior: .- "'Shell resembling ^. oil oat a [-nomey and 

 Holmes (l)J, "but flatter; not plicate, "but gently v/aved distally; 



(1). Pleioc. Pes. South Carolina, p. 19, pi. 6, figs. 4-6, 1855. 



surface ri::dially oeulptured with minute, almost microscopic, 

 threads, v/hich are frequently interrupted, when the termination 

 of the nvorA'^al loart of the thread is swollen, resembling a min- 

 ute head or pustule; interior resenbling P. plicata . but the hinge 

 wesiker, the amorphous irregularities confined to a. very small 

 ST^aoe near the umbo, ^nd inconspicuous; crura of the lower vnlve 

 small, forming an acute angle, well elevated, the socket for their 



reception on the or^posite valve shallow, Alt. about 50, lat. 50, 

 diam about 8 mm." 



"Thic form is distingi:;ishable at once by its peculiar sur- 



