78 



BuiviyETiN 39 



shorter than the narrow aperture; nucleus of about 3^ smooth, 

 convex whorls, the last >^ turn being very finel}^ and closely rib- 

 bed; there are 3% post- nuclear w^horls; sculpture consists of 

 narrow, slightly oblique ribs w^hich pass across the spire-whorls 

 from suture to suture and on the last whorl follow down on the 

 anterior canal to its tip; there are 8 ribs on the last whorl; the 

 spaces between the ribs are wide, flat and smooth; the tops and 

 sides of the ribs themselves are carved or etched vv^ith fine, sub- 

 obsolete spiral lines; aperture linear-elliptical, the outer lip some- 

 what thickened by the last rib, but smooth within; anterior ca- 

 nal long straight. 



Height 9, diameter 3.50, last whorl 7mm. 



Gatun Stage: Po'rt Limon. 



Genus BORSONIA Bellardi 



Borsonia cocosnsis, n. sp. Plate 5, figures 23, 24 



Shell small, biconic; whorls about 7; nucleus of 2, nearly 

 smooth whorls, follov^ed by 5 strongly shouldered post-nuclear 

 whorls, the angle of which on the spire- whorls comes just 

 above the lower suture; above the shoulder, the whorls 

 are flat or slightly concave to the upper suture; sculp- 

 ture with a double or triple beaded cord on the peri- 

 phery and with alternating beaded spirals both above and below; 

 on the last whorl, the primary spirals number 15 or 16, above 

 the shoulder 3 or 4; the suture is bordered in front by a strong 

 cord; pillar long, slightly twisted in front and with 2 sharp, pli- 

 cations; the anal sinus lies on the peripheral angle as in typical 

 Turris. 



Length 16, diameter 8, last whorl 11 mm. 



The present species is based on two specimens from Coco 

 Plum about 30 miles east of the city of Bocas del Toro. The 

 B. varicosa Sowerby from the Dominican Miocene, is a related 

 species, differing in its porportionately longer spire. 



Gatuii Stage: Coco Plum. 



