40 



Bulletin 39 



Terebra estreSiarsa, n. sp. Plate i, figures 9, 16 



Shell small; nucleus of three smooth tapering whorls; post- 

 nuclear whorls about 9, sculptured with a faint sutural sulcus, 

 which is lacking or nearly so from the early whorls; axial sculp- 

 ture of about eleven, straight or slighth^ oblique ribs which pass 

 from suture to suture; but are nearly lacking from the base; 

 spirals lacking or very faint on the spire-whorls, so that they ap- 

 pear smooth and solid; the base of the last vv^horl is strongly con- 

 tracted and shows four or five, very faiut spirals; pillar straight 

 and smooth; beak twisted. 



Length 7.5, diameter 2.5 mm. 



This is a small species of rather solid appearance, strong 

 ribs, but otherv/ise nearh^ smooth whorls. The spirals are very 

 faint and are seen best only when viev/ed at right angles to the 

 source of light. Our specimen came from the Estrella River. 



Gatun Stage: Zone 7, Estrella Riv^r, C. R. 

 Terebra costaricensis, n. sp. Plate i, figure 19 



Shell small and slender, with about three, long, tapering 

 smooth, nuclear whorls; post-nuclear whorls eleven; sutural 

 band rather large and prominent, strongly tuberculated; the 

 spire- whorls are slightly concave and have at their base or just 

 above the suture, a revolving series of tubercles, which are the 

 enlarged bases of the longitudinal ribs; longitudinal ribs on the 

 last whorl number about twelve, are nearly straight and large 

 and strong on each side of the suture, low and weak in the mid- 

 dle of the whorls; the surface of the whorls are otherwise smooth 

 or in some shells feebly spiralled; base slightly rounded with 

 eight or more sjDirals w^hich become finer as they approach the 

 canal; the longitudinal ribs are continued across these spirals. 

 Length 13, diameter 3 mm. 



The above description is based mainly on two specimens 



