- 211 - 



tn.re on the -<'''^ Tr.-iyo.q ip ^-.n^'-pri. On the left valve, since the 

 interspaces are v/ider than on tL.e rif;^ht, the cone entrio sculpture 

 is more lorominent and the arched, cro?;ded growth lines on the rihs 

 are more Gonstantlj^ -o^ ^..^ ...it . Left valves are usually more inequi- 

 lateral than right ones. The rihs of immature left valves are 

 less rounded, almost square, distally than on adults; while young 

 right valves differ from adults in having the ^^■'-■: i'^-,- --r and the 

 interspaces wider. 



The strongly inflated right valves, with hirh, "broad, sharp- 

 ly chiseled rihs and the decidedly less convex left valves, with 

 lower, more rounded rihs are readily distinguishable from the assoc- 

 iated Pectens. The Gatun F. le vice status Toula (l) reaches a lar;?- 



P.l 7 



ize, is loR':- -^onvex, v/ith more numerous (twenty-one), slightly 



(1). Jahrh. K.-k. s-eol. Heichsanstalt, vol. 58, p. 71?, pi. 26, 

 figs. 4-6, 1908. 



narrov/er andlov/er radialc. Right valves may be confused with the 

 young of P. operc:-lariforrais Toula (£), from the same locality, but 



{2). If^em, :ji;. 712-715, pi. "■, n~. 7.. 



the C-atun form is less inflated, ^:ri. th more nuraerous (twenty-five) 

 narrower radial s, narrower and shallov,-: r interspaces; since the 



