258 Bulletin 39 430 



Length 30. 50, height 15.00, diameter of the left valve 

 3.00 mm. 



Gatun Stage: Mt. Hope, C. Z. 



Genus SEMELE, Schumacher 



Semele laevis Sowerby, van costaricensis, n. var. Plate 29 figure I 



Cf. Ainphidesma Icevis Sowerby, in Reeves, 1853, Conch. Icon., pi. 7, 

 fig- 50. 



Shell large, subelliptical, but slightly convex; beaks very 

 nearly central, the posterior side wide and well rounded, the an- 

 terior somewhat narrowed, contracted and. slightly the longer; 

 the surface is nearly smooth and porcellaneous, faintly marked 

 on the anterior and posterior extremities by fine, concentric 

 lines. 



Length 72, height 65.50, semi-diameter 8 mm. 

 This large Semele is quite common in the Lower Gatun beds 

 of the Banana River. It is closely related to the recent Pacific 

 ^. Icevis Sowerby, but differs in being slightly longer and more 

 evenly rounded at its posterior extremity. 



Gatun Stage: Hill No. j, Bajiana River. 

 Hill la, Banana River. 



Semele Sayi Toula Plate 29, figure 8 



Semele Sayi Toula, 1908, Jahrb. der K-K Geol. Reichsanstalt, Wien, 



vol. 58, p. 730, pi. 28, fig. 17. 

 Semele Sayi Brown and Pilsbry, 1911, Proc. Acad. Nat. Sci. Phlla. 



vol. 63, p. 368. 



Shell convex, rather thin, with the umbos nearly central. 

 The anterior side is somewhat narrow or contracted, and round- 

 ed at its extremity. The surface is sculptured with fine, hair- 

 like, concentric threads. The species was described by Toula 

 from the Canal Zone. Our record from Costa Rica is based on a 

 single, imperfect specimen from Sousi creek, where it occurs as- 

 sociated with dementia, Chione viactropsis and Turritella altilira 



