239 Costa Rico Mioce^ne: — Oi.sson 67 



crossing the ribs on the spire-whorls and very much finer ones in 

 the anal fa.sciole; the last whorl shows about 10 spirals together 

 with others on the canal; aperture elongate with the anterior 

 canal rather long and straight. 



Length 19, diameter 6.5 mm. 



Like the Drillia co7isors in form, this species is distinguish- 

 ed by its fewer ribs and shallower anal faciole. The ribs on the 

 earlier whorls are oblique, but become very nearly straight and 

 vertical on the later. 



Gatun Stage: Port Limo7i. 



DriJiia bocatoroensis, n. sp. Plate 5, figure 6 



Shell of medium size, solid and strongly sculptured with 

 ribs and spirals; whorls about 11, the nucleus eroded in the type 

 specimen; fasciole occupying about 1-3 of the width of the spire- 

 whorl, with a large sutural cord above which the edge of the su- 

 ture is finely and regularly beaded or granulated; the surface of 

 the fasciole is slightly undulated by the obsolete ends of the ribs, 

 otherwise smooth; axial ribs about 8 on the last whorl, straight 

 and nearly in line across the face of the spire-whorls to the apex, 

 but interrupted and lacking from each fasciole; spiral sculpture 

 of the few raised cords with wider interspaces; there are 3 

 spirals on the spire- whorls, about 6 on the last, with 9 more on 

 the anterior canal; the interspaces in addition carry fine and sub- 

 microscopic spiral lines; the base of the last whorl is somewhat 

 constricted with a short anterior canal. 



Length 23, diameter 8, last whorl 13.5 mm. 



From the several species of f usoid Pleurotomids in the Gatun 

 beds of Panama and Costa Rica, this species differs in its heavy, 

 persistent ribs and sharp spiral sculpturing. The fasciole is 

 nearly smooth, bordered above by a heavy sutural cord. 



Gatu7i Stage : Bocas del Toro. 



