46 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I25 



right angles to that of the postnuclear spire, in the first whorl of 

 which the nucleus is about one-third immersed. The postnuclear 

 whorls are flattened and crossed by strong, retractively slanting axial 

 ribs, which have the same strength from the summit to the periphery. 

 Of these ribs 12 are present upon the second whorl, 13 upon the 

 third and fourth, and 14 upon the rest, except for the last, which has 

 16. The intercostal spaces are about as wide as the ribs and are 

 crossed by six spiral pits, of which the first and the last two are 

 finer than the rest and subequal. The second and fourth are of equal 

 strength and about two and one-half times as wide as the first, fifth, 

 and sixth, while the third is still wider. The spacing and details are 

 best realized by viewing the sketch, plate 8, figure ib. Base hemi- 

 spherical, smooth. Suture moderately strongly impressed, rendered 

 wavy by the summit of the strong axial ribs. Aperture rather short, 

 obliquely oval, columella slender, curved, provided with an oblique 

 fold a little below its insertion ; outer lip thin. 



The type, U.S.N.M. No. 561645, comes from the PHocene deposits 

 of North St. Petersburg, Fla. It has 9.5 postnuclear whorls and 

 measures: Length 4.2 mm., diameter i.i mm. 



This species differs from Pyrgiscus silenusi (p. 45) by its more 

 conic outline, much stronger axial ribs, and detailed spiral sculpture. 



PYRGISCUS APOLLOI, new species 

 Plate 8, figures 2a, b 



Shell small, turrited, stout, cream-colored. Nuclear whorls 2.3, 

 strongly rounded, forming a moderately elevated helicoid spire whose 

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

 of which the nuclear spire is slightly immersed. The postnuclear 

 whorls are strongly rounded, and crossed by strong, broad, almost 

 vertical axial ribs, of which 14 are present on the first and 16 on all 

 the rest of the whorls except the last, which has 18. The axial ribs 

 are a little wider than the spaces that separate them and are of the 

 same strength from summit to the periphery. The intercostal spaces 

 are crossed by seven deep, broad spiral pits, of which the first, second, 

 and fourth are of equal width and a little more than half the width of 

 the rest which are subequal. (See sketch, pi. 8, fig. 2b.) Suture 

 strongly constricted, rendered decidedly wavy by the summit of the 

 strong axial ribs. Base hemispherical, smooth. Aperture obliquely 

 oval, columella with an oblique fold a little below its insertion, outer 

 lip fractured in the type. 



The type, U.S.N.M. No. 561646, comes from the Pliocene of North 



