345 Costa Rica Miocene — Ols.son 173 



Genus LEDA Schuuiacher 



Leda Balboae Prown and Pilsbry " Plate i8, figure 15 



Leda Balboa; Brown and Pilsbry, 191 1, Proc. Acad. Nat. Sci. Phila. , 

 vol. 63, p. 362, pi. 27, fig. 8. 



This species is fairly common in Costa Rica, but generally 

 smaller than in the Canal Zone, where it frequently reaches a 

 length of 22 mm or more. Its valves are moderately convex and 

 regularly sculptured with even, close, concentric riblets which on 

 the center of the shell disk ma)' be slightly appressed. The 

 escutcheon is well-defined and similiarly sculptured with the rib- 

 lets running parallel to the hinge margin. 



Gatun Stage: Gatun, C. Z. 



Coll. z. East Grape Point Creek. 



Zonie G, Saury Creek. 



Qui tan a Creek. 



Hill No. J, Banana River. 



Leda Davilae, n. sp. Plate 18, figure 20 



Shell small, solid, strongly convex; the beaks nearl}^ cen- 

 tral; the rostrum is short, pointed and sharply defined from the 

 rest of the shell disk by a high, cord-like ridge; the anterior end 

 is bluntly rounded and carries 2, low flexures from the beaks to 

 the anterior ventral extremity; lunule small and narow, lacking 

 the concentric ribs and sculptured with small, pustular-like 

 ridges passing at right angles to the hinge-line; the sculpture con- 

 sists of about 30 concentric riblets which are somewhat larger 

 and with deeper interspaces on the umbos; the interspaces show 

 on the umbos and along the anterior slope, fine, radial lines or 

 punctations; interior of the shell cavity deep, with a heavy 

 hinge; the anterior and posterior sets of teeth number about 13 

 or 14, are high and V-shaped. 



Length 5.75, height 4.00, semi-diameter 1.75 mm. 



