24 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I25 



nate at the periphery. They are about as wide as the ribs. The suture 

 is well impressed and rendered sinuous by the ribs. The periphery is 

 well rounded. The base is short, well rounded, smooth. The aperture 

 is obliquely subquadrate; the columella is slender and bears a feeble 

 fold near its insertion ; the outer lip is thin. 



The type, U.S.N.M. No. 561620, comes from the Pliocene beds 

 of North St. Petersburg, Fla. It has 8.6 whorls remaining and meas- 

 ures: Length 6.2 mm., diameter 1.4 mm. An additional specimen is 

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



TURBONILLA (CHEMNITZIA) HESPERUSI, new species 

 Plate 4, figure 2 



Shell cylindric, of medium size, cream-yellow. Nucleus and early 

 postnuclear whorls decollated, the whorls remaining form a cylindric 

 spire. The postnuclear whorls are flattened and crossed by decidedly 

 protractively slanting axial ribs, which are equally strong from the 

 summit to the periphery. Of these ribs 14 are present on the penulti- 

 mate whorl of the type; on the last half of the last whorl the ribs 

 become less strong and more numerous and closely spaced, indicating 

 a senescent stage. The intercostal spaces are a little narrower than 

 the ribs, the gouged-out part, like the ribs, terminating at the periph- 

 ery. Suture well impressed, rendered wavy by ribs. Periphery well 

 rounded. Base hemispherical, smooth. Aperture obliquely subquad- 

 rate; columella slender, provided with a weak fold a little anterior 

 to its insertion. 



The type, U.S.N.M. No. 561621, comes from the Pliocene deposits 

 of North St. Petersburg, Fla. It has 8.4 whorls remaining which 

 measure: Length 5 mm., diameter i mm. An additional specimen is 

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



TURBONILLA (CHEMNITZIA) ATLASI, new species 



Plate 4, figures Sa, b 



Shell elongate-turrited, of medium size, cream-yellow. The nucleus 

 consists of a little more than two strongly rounded whorls, which form 

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

 turns, in the first of which the nuclear spire is half immersed. The 

 postnuclear whorls are flattened and crossed by strong, moderately 

 protractively slanting axial ribs, which are of equal strength from the 

 summit to the periphery where they terminate. The last whorl of 

 the type shows 15 axial ribs. The intercostal spaces are a little nar- 



