42 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I25 



is at right angles to that of the postnuclear whorls, in the first of 

 which it is about half immersed. The postnuclear whorls are only 

 slightly rounded; they are crossed by strong vertical axial ribs, of 

 which 12 are present upon the second to sixth, 14 upon the seventh, 

 and 15 upon the last whorl. These ribs become stronger and wider 

 on succeeding turns, and they are of the same strength from the 

 summit to the periphery. The intercostal spaces are as wide as the 

 ribs and bear six deeply impressed spiral pits which are of equal 

 strength but not of equal spacing (see sketch, pi. 7, fig. 5b). Suture 

 moderately impressed, rendered wavy by the summit of the ribs. Base 

 hemispherical, smooth. Aperture obliquely oval, columella slender 

 with an oblique fold near its insertion. Outer lip thin, parietal wall 

 covered with a thin callus. 



The type, U.S.N.M. No. 561638, comes from the Pliocene of North 

 St. Petersburg, Fla. It has 9.5 postnuclear whorls and measures: 

 Length 3.9 mm., diameter 0.9 mm. 



This species resembles Pyrgiscus thestiitsi (p. 41) but is easily 

 distinguished from that by its much more slender form. 



PYRGISCUS CLIONAE, new species 

 Plate 7, figures 4a, b 



Shell small, turrited, slender, cream-colored. Nuclear whorls decol- 

 lated. The postnuclear whorls are almost flattened and crossed by 

 strong vertical axial ribs, of which 12 are present upon the first to third 

 of the remaining turns, 13 upon the fourth, 14 upon the fifth, 16 upon 

 the sixth, and 18 upon the last whorl. These ribs are of the same 

 strength from the summit to the periphery. The intercostal spaces 

 are as wide as, or a little wider than, the ribs ; they are crossed by six 

 deeply impressed spiral pits, which are not of the same strength or 

 spacing (see detailed sketch, pi. 7, fig. 4b). Suture moderately im- 

 pressed, rendered wavy by the summit of the ribs. Base hemispherical, 

 smooth. Aperture obliquely oval; columella slender, reflected, and 

 provided with an oblique fold a little below its insertion; outer lip 

 thin, parietal wall glazed with a thin callus. 



The type, U.S.N.M. No. 561639, comes from the Pliocene of North 

 St. Petersburg, Fla. It has 7.5 postnuclear whorls remaining and 

 measures : Length 3.5 mm., diameter i mm. 



This species resembles most nearly Pyrgiscus tellusae (p. 41) but 

 is readily distinguished from it by its less strong sculpture and more 

 uniform spiral markings. 



