317 



Costa Rica Miocenk — Olsson 



very much larger, broader and the longitudinal costae are more 

 rib-like, continued across the whorls, crossing the interspaces as 

 well as the spiral cords. 



Gatun Stage: Bajiana River. 



Clava aiajuefa, n. sp. Plate lo, figure 30 



Shell small, slender; whorls 12 plus, the apex broken; the 

 sides of the whorls are straight and form the narrow, tapering 

 spire; sutures indistinct; the sculpture consists of nearly equal 

 ribs and spiral threads; the early spire- whorls have 3, equal, 

 spiral threads, separated by interspaces as wide as the spiral 

 threads and deep; on the later Vv^horls fine, intermediate threads 

 appear in the interspaces and a fourth large spiral in the lower 

 suture; the spirals are crossed and strongly beaded by straight or 

 slightly curved, longitudinal ribs, which number on the last 

 whorl about 25 or 24; heavy and thickened resting marks ap- 

 pear on the later whorl on each volution; the aperture is broken, 

 the columella straight and with a single small fold. 



Height 17 mm, diameter 6 mm. 

 A small and finely sculptured species, represented by the 

 single type specimen. 



Gatun Stage: Middle Creek. 



Genus SERPULORBIS Sassi 

 Serpulorbis papulosa Guppy Plate 12, figure i 



Vermetus papulosus Guppy, 1866, Quart. Journ. Geol. Soc. lyondon, 



vol. 22, p. 292, pi. 17, fig, 3. 

 Vermetus papiUosits Guppy, 1876, Quart. Journ. Geol, Soc. London, 



vol. 32, p. 519. 



Sespulorhis papulosa Maury, 1917, Bull. Amer. Pal,, vol. 5, p. 291, pi. 

 22, fig, 10, 



Considerable variation may be seen in the Costa Rican shells, 

 from specimens in which the sculpture is quite coarse and with 

 the interspaces between the main cords carrying only one strong 



