425 



Costa Rica Miocene — Olsson 



253 



the shell may sometimes appear nearly smooth and polished 

 especially on the umbonal areas; hinge of the left valve with a 

 bifid anterior cardinal, a small posterior and 2 laterals; the an- 

 terior adductor is bordered on the posterior side by a thickened 

 internal ray; pallial sinus long, ascending above in the middle 

 of the shell and touching the anterior adductor scar. 



Length 34, height 19.5, semi-diameter 3.50 mm. 

 Gatun Stage: Gahm, C. Z. 



Watei'- Cay. 



Chiriqui Lagoon and O r on li creek {Gabb) 



Subgenus AMGULUS, Mergerle 



Section AI^OULUS, s. s. 

 Tellina umbra Dall Plate 26 figures 12, 15 



Tellina {Angulus) umbra Dall, 1900, Trans. Wagner Free Inst. Sci. , 

 vol. 3, pt. 5, p. 1033, pi. 46, fig. 13. 



The Costa Rican specimen consists of a small individual 

 with both valves. It is somewhat smaller than typical umbra, 

 from the Upper Chesapeake Miocene of the Carolinas, but agrees 

 in form and in the fine surfrce sculpturing. 



The Tellina umbra is a common fossil in the Upper Chesa- 

 peake Miocene of the eastern United States and in the Pliocene 

 of Florida, It is closely allied to the recent Tellina sybaritica 

 Dall of the West Indies, differing most importantly in its less an- 

 gular posterior extremity. 



The Costa Rica specimens measures: 



Length 8.00, height 4.15, diameter 2.25 mm. 



Gatu7i Stage: Coll. 4., East Grape Point creek. 



Section SCISSULA, Dall 



Tellina cercadica Maury 



Tellina {Scissula) cercadica Maury, 1917, Bull. Amer. Pal., vol. 5, p. 

 388, pi. 38, fig. 9. 



