throiip-hont aiad ooaolete dis-^a'l^', sculpt ux-'j. bj? feeble eontinu- 

 atio.is of the concentrio rii,^ae; escutcheon ; ' from 



the ''nho to the ventrel enr' of t>c ■*Tor'te'"''ior 



roil. ec. es-i-ina _ca:e3e.at, b e cj o:;ii n^: oo^c„e';e co".7i:r;-- -■L'^j^'-; 



external surface sculptTU-er! with concentric rno-ae, usually crowd- 

 ed toward the margins; hinge strong, the left anterior lateral 

 stroiig and promineiTG , the. right posterior cardinal bifid; pallial 

 sinus deep and broad. 



Dlraensions .- lenght, 51 nm. ; alt,, 70,5 ram.; semidiam., 

 10.5 mm. 



""-ccs-rks .- ?. planivieta is one of the most abundant of the 



Veneri^.ae. ■^-'■:^.'^"t for the ur^^-al variation in the width of the 

 concentric rugae and an occasional irregularity in their arrange- 

 aent, the characters are quite unifom. It is characterized by 

 its relatively lai---ft r-ise, height and strong, r ef " "i .'^' '% concen- 

 tric sculpture. 



A closel;. related amdescribed form 0GCu.rs in the Iniplin 

 fauna. P. c-^ra "Brown e.v^. "Pilsbr" (l ) "rora the untu-,- beris, is 

 sraallcr, less elongated ( soae of the s leciraens are i.rve elongated 



(1). Proc. Acad. _'>t. ^^ci., ^>t "^ >-■ Delphi c, ::.!. V, . ■/", pi. 

 20, fig. 3, 1911. 



than the one figured), with slightl. " rect uni- 



bones and finer sculntujce. Crabb ' s Oosta '\ican Pliocene P. gup- 



