152 



Bulletin 39 



3«4 



cords on mature shells are small and but slightly heavier than the 

 spiral threads on the concave band. 



This type replaces the chiriqiiiejisis in the Gatun sandstones 

 in the area of Upper Hone Creek and Boucary Creek. It is often 

 extremley abuadant, associated with the Turritella ^atunen- 

 sis. 



Gatun Stage: Upper Hone and Boucary Creeks. 

 Turritella exoleta Linnaeus, var. limonensis, n. var. Plate 14, figs 2, 3 



Shell turreted, the whorls increasing more rapidly in diame- 

 ter than typical exoleta; the nucleus is small, immediately follow- 

 ed by whorls carrying a median carina which gradually becomes 

 more anterior in position and later the lower carina of the adult 

 sculpture; the whorls are deepl}'- concave or excavated about the 

 middle between 2 principal carinae; on the last whorl there is 

 seen to be a third carina which is concealed in the suture; the su- 

 tures are excavated, becoming generally deeper with age; the 

 surface is nearly smooth, except for very faint spirals and rough 

 growth lines which may be raised and sublamellose on the medi- 

 an concave zone. 



Height 40 (6 later whorls) diameter 17.50 mm. 

 Height 35 (10 earlier whorls) diameter 10 mm. 



This is probably a distinct species from the recent West In- 

 dian Turritella exoleta lyinnaeus, differing in its more rapidly ex- 

 panding whorls. Faint spirals may generally be seen covering 

 the entire shell and the growth lines become raised and sublamel- 

 lose in the concave medial zone. It is a common shell in the cor- 

 alline phase of the Gatun at Port Limon and elsewhere. 



Gatun Stage: Port Limon. 



Bocas del Toro. 



Turritella oreodoxa, n. sp. Plate 14, figure i 



Shell large, solid and very slender; whorls numerous and 

 each but slightly larger than the preceding, slightly concave or 

 constricted about the upper 1-3, above which the edge of the 



