40 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, I25 



The type, U.S.N.M. No. 561631, comes from the Pliocene of North 

 St. Petersburg, Fla. It has 8 postnuclear whorls and measures: 

 Length 4.9 mm., diameter i mm. U.S.N.M. No. 561632 contains 

 seven additional specimens from the same source, and seven more 

 are in the collection of the A.N.S.P. 



The strongly rounded whorls and strong axial ribs will distinguish 

 this species from the other five spirally pitted forms. 



PYRGISCUS VENUSAE, new species 

 Plate 6, figures Sa, b 



Shell moderately large, very regularly turrited, cream-yellow. The 

 nucleus consists of about 2.4 well-rounded whorls that form a low 

 heUcoid spire whose axis is at right angles to that of the postnuclear 

 spire, in the first whorl of which the nucleus is about one-third im- 

 mersed. The postnuclear whorls are flattened and crossed by very 

 strong vertical axial ribs, of which 12 are present on the second to 

 eighth whorl, 14 upon the ninth, and 16 upon the last whorl. The 

 axial ribs extend equally strong from the summit to the periphery. 

 The intercostal spaces are a little narrower than the ribs and are 

 crossed by fine strong spiral pits, which are of almost equal spacing 

 (see detailed drawing, pi. 6, fig. 5b). The suture is moderately im- 

 pressed and rendered wa\'y by the axial ribs. The base is hemispherical 

 and smooth. The aperture is subquadrate, the columella is reflected 

 and bears a strong fold near its insertion, the outer lip is thin, and the 

 parietal wall is covered by a thin callus. 



The type, U.S.N.M. No. 561633, comes from the Pliocene of 

 North St. Petersburg, Fla. It has 11 postnuclear whorls and meas- 

 ures: Length 5.1 mm., diameter i.i mm. U.S.N.M. No. 561634 

 contains two additional specimens from the same source, and two 

 more are in the collection of the A.N.S.P. 



PYRGISCUS TITYUSI, new species 

 Plate 7, figures la, b 



Shell moderately large, turrited, cream-yellow. The nucleus con- 

 sists of 2.5 whorls that form a low helicoid spire whose axis is at right 

 angles to the axis of the postnuclear whorls, in the first of which it 

 is about one-third immersed. The postnuclear whorls are flattened 

 and crossed by moderately strong axial ribs, which are of the same 

 strength from summit to suture; of these ribs 16 are present upon 

 the second to sixth whorl. On the last turn, which is slightly inflated, 

 the axial ribs become gradually weaker, much more numerous, and 



