40 Bulletin 39 a is 



Terebra estreiZana, 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 slightlj' oblique ribs which pass 

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

 spirals lacking or ver}^ faint on the spire-whorls, so that they ap- 

 pear smooth and solid; the base of the last whorl is strongly con- 

 tracted and shows four or five, very faint 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 otherwise nearly smooth whorls. The spirals are very 

 faint and are seen best only when viewed at right angles to the 

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



Gatun Stage: Zone 7, Estrella Rive.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 spirals which become finer as thej^ 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 



