301 



Costa Rica Miocenk — Oi^sson 



129 



Xength 15.5, diameter 7.5, spire 8, aperture 8 mm. 

 A species with an Anadizs-like sculpture, the ribs and gen- 

 erally the spirals being persistent. The body-whorl is flattened 

 or slightly contracted about the middle, but less so than in the 

 following variet}^ A long, tapering and nearly smooth spire as 

 in the preceding S. cricaviola but much more slender and at- 

 tenuated. 



Gatun Stage: Headwater of Middle Creek, C. R. 

 Strombitia costaricensis, var. mysanica, n. var. Plate 10, figures 26, 27 



Shell ovate, with a long, conic spire of 8 or more whorls; 

 last whorl strongly contracted or indented about the middle; the 

 first 3 whorls or more (apex broken) are smooth or sculpturless; 

 on the following 3 whorls, the sculpture is largely of numerous, 

 straight rib-like costae, the spirals being only very faint and in- 

 distinct; on the last v^^horl the ribs number about 14; spirals 

 about 9 on the penultimate whorl as faint raised threads and on 

 the last whorl may be lacking from the middle or contracted 

 zone; aperture linear-ovate, a thickened outer lip with 3 faint 

 denticles below the upper notch; canal straight. 



I^ength 15, diameter 6.5, spire 13, aperture 8 mm. 



Probably a distinct species from the preceding and differing 

 in its more evenly tapering and more strongly sculptured spire, 

 and deeply contracted body-whorl. It resembles somewhat the 

 figure of ^. cartageyisis Brown and Pilsbry from Colombia, but is 

 smaller and has more numerous ribs. The periphery of kS. car- 

 tag ensis is rounded. 



Gatun Stage: Banana River^ C. R. 



East fork of Red Cliff Creek. 



Stromblna sincola, n. sp. Plate 10, figures 19, 21 



Shell small, with a large, conic spire and a dorso-ventrally 

 flattened body-whorl; whorls about 8, the first 3 belonging to the 

 small, smooth, pointed nucleus; sculpture of the post-nuclear 

 whorls of numerous, straight, strong, longitudinal ribs, which are 



