1 92 Bulletin 39 364 



the right valve with narrow ribs, separated by wide inter- 

 spaces. 



B. The intervals between the ribs on the posterior 

 half of the right valve with small (sometimes faint) interstitial 

 threads. Ribs about 29. 



Aj'ca Lloydi, n. sp. 

 BB. The intervals between the ribs on the posterior 

 half of the right valve smooth; ribs 25, shell usually- 

 larger. 



Area Hindsi, n. sp. 



Area Pittieri Dall Plate 24, figures 2-6 



Area [Seapharea) Pittieri Oall 1912, Smith. Misc. Coll., vol. 59, No. 2, 

 p. 9. 



This is a common species in the Gatun beds of the Banana 

 River. The ribs of the 2 valves are similarh?- sculptured but 

 somewhat less strongly on the right. The umbos are high. 

 The posterior extremity is pointed and produced so that the out- 

 line of the shell is more elongate than in the following species: 

 Length 25, height 25, diameter 26 mm. 



29 28 semi-diameter 14.5 mm. 



Gatun Stage: Hill la, Banana River, j. 

 Zone E, Saury Creek. 

 Rio Betey. 

 Coll. 7, Pumbri Creek. 



Area Lloydi, n. sp, Plate 24, figures 10-12 



Shell small, cordiform, covex, subrectangular in outline but 

 with the left valve somewhat more pointed at its posterior-ven- 

 tral extremity; anterior side well rounded; posterior side straight 

 and meeting the basal margin at an angle of about 75 degrees; 

 umbonal angle rounded; the left valve has 29 ribs of which 9 

 are found on the posterior- dorsal slope; the ribs of the left 

 valve are strongly beaded or granulated, and separated by inter- 

 spaces of about their own width; on the right valve, the first 10 

 anterior ribs are strongly beaded; the next set as far as the um- 



