144 



BULLETIN 39 



Spire- whorls is convex with an occasional hump- like resting mark; 

 the sculpture consists of primary spiral threads between which 

 lie I, 3, or more finer secondaries; the earlier spire-whorls have 

 heavy ribs but they become replaced on the later by simple gran- 

 ulations on the primary spirals; a narrow, sloping band borders 

 the anterior side of the suture and carries finer, non-beaded spiral 

 threads: below this band, the later spire- whorls bear about 4 

 beaded, primary spirals and finer secondaries; the last whorl shows 

 6 primaries together with other spirals on the base and canal; 

 aperture subcircular, with a moderately expanded outer lip, obli- 

 quely produced anteriorly. 



Height 28, diameter 10.5, aperture 8 mm. 



The general form and sculpture of this species is that of the 

 recent West Indian C. eburneurn Bruguiere. The fossil shell is 

 larger, more slender and differently sculptured. 



Gatun Stage: Coll. 6, Red Cliff Creek. 



Genus CLAVA Martyn 



Clava costarlcana, n. sp. Plate 10, figures 3, 4 



Shell of medium size, cerithoid; whorls about 15, the early 

 spire-whorls very small; the last whorl carries a large hump on 

 the ventral side of the shell to the right of the aperture, so that 

 the shell appears flattened on this side; the sculpture consists of 

 strong spiral cords which are coarsel}^ granulated by small, close- 

 ly spaced longitudinal costae; the upper spiral cord bordering the 

 suture is somewhat larger than the other; there are 3 spirals be- 

 tween the sutures of the spire-whorl and 6 on the last whorl with 

 additional smaller ones on the base of the shell; the outer lip is 

 broken on all our specimens; the columella carries 2 strong 

 folds. 



Height 40, diameter 15 mm. 



41, 14 mm. 



This species bears some resemblance to the C. caloosaensis 

 Dall from the Pliocene of Florida. The Costa Rican shell is 



