393 



Costa Rica Miocene — Olsson 



22 I 



A small, subcircular shell, neatly sculptured with fine, con- 

 centric threads. D. minor Dall from the Bowden beds is strong- 

 ly oblique. 



Gatun Stage: Water Cay. 



Genus fV!YRTAEA, Turton 

 iVlyrtaea limoniana Dall Plate 32, figures 11, 23 



Myrtcea limoniana Dall, 1903, Trans. Wagner Free Inst. Sci., vol. 3, 

 pt. 6, p. 1358, pi. 52, fig. 10. 



A small, thin and slightly convex shell, its surface sculptur- 

 ed with fine, thin and sharp, elevated, concentric lamellae. We 

 have several specimens from the coral limestones of Port Limon 

 as well as a larger specimen from Zone 4, of Red Cliff Creek. 

 This later shell measures: heigth 9.50, length 10.00, diameter of 

 the right valve 2.50 mm. It occurs also in the Bow^den beds of 

 Jamaica. 



Gatim Stage; Port Limon. 



Coll. ^, Red Cliff creek. 



Genus PHACOIDES, Blainville 



Subgenus CALLUCINA, Dall 



Phacoides radians Conrad, var. medioamericanus, n. var. Plate 32 fig. 16 



The Phacoides radians Conrad is a fossil of the Upper Ches- 

 apeake Miocene of the Carolinas but has continued through the 

 Pliocene to the recent fauna. The Costa Rican fossils differ from 

 typical radians in having their umbos sculptured with about 

 6 ribs much stronger than the concentric, while in t5^pical 

 radians, the ribs are more numerous and about equal to the con- 

 centric lines. The medioaviericamis is also smaller as may be 

 seen in the measurements given below, while radians is large 

 (20 mm) and often quite convex. 



Length 9.5, height 9, semi-diametes 2.5 mm. 



