233 



Costa Rica Miocene— Oi^sson 



6i 



nearly total lack of spiral sculpturing. The species is named 

 for Dr. W. H. Dall of the National Museum, the author of the 

 genus A 7ic7st7'osyri?ix, 



Gatun Stage: Toro Cay, Water Cay, Panama. 



Genus m\\X.\k Gra}^ 

 Drillia venusta, Sowerby Plate 4, figure 9 



Plciirotouia venusta Sowerby, 1849, Ouart. Jour. Geol. Soc. London, 



vol. 6, p. 50, pi. 10, fig. 7. 

 Pteurotonia veiuistuiu, Guppy, 1866, Quart. Jour. Geol. Soc. London, 



vol. 22, p. 289. 



Tiirris {Drillia) venusta, Gabb, 1873, Trans. Amer. Phil. Soc, vol. 

 15, p. 208. 



Pteurotonia venusta, Gupp}^ 1S76, Quart. Jour. C4eol. Soc. London, vol. 

 32, p. 527. 



Pteurotonia venusta, Guppy and Dall, 1896, Proc. U. S. Nat. Museum, 

 voL 19, p. 305. 



Drillia venusta Maury, 1917. Bull. x\nier. Pal., vol. 5, p. 216, pi. 8, 

 figs. 13, 14. 



The Drillia venusta and consors of Sowerb}^ are the two 

 commonest Pleurotomids in the Gatun beds of Costa Rica. 

 Both are characterized by a neat, regular and reticulate sculp- 

 ture of spirals and axial ribs. In v^viusta, the anal fasciole is 

 narrow, and appears as a deep constricted zone, encircling the 

 upper part of each whorl. The spirals are narrow bands, pro- 

 duced between deep, incised lines and in typical specimens num- 

 ber on the last whorl about i8. The canal is rather long and 

 usually more or less twisted. 



Drillia venusta, occurs also in the Miocene of Jamaica, 

 Trinidad and in Santo Domingo. 



Gatun Stage: Gatim, C. Z. 



Baiiajia River, Port Limon. 



Drillia consors, Sowerby Plate 4, figures 8. fu, 13 



Pteurotonia eonsors, Sowerby, 1849, Quart. Jour. Geol. Soc. London, 

 vol, 6, p. 50. 



