34 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I25 



MORMULA PILSBRYI, new species 

 Plate 6, figures 2a, b 



Shell elongate-turrited, stout, stained with brown. The nucleus 

 is decollated in both specimens seen. The postnuclear whorls are 

 flattened and crossed by decidedly retractively slanting, crowded, low 

 axial ribs, of which 20 are present upon each of the remaining turns. 

 These ribs are of the same strength from the summit to the periphery, 

 where they terminate. At irregular intervals some of the ribs become 

 thickened to form a varix. The intercostal spaces are narrower than 

 the ribs and are crossed by six strongly incised pits, of which the 

 first two below the summit are about half as wide as the fourth and 

 fifth, while the third and sixth are much broader and of about equal 

 width. The spacing of the pits is subequal. The suture is shallow 

 and is rendered wavy by the summit of the axial ribs. The periphery 

 is well rounded. The base is hemispherical and marked by a few ill- 

 defined spiral striations. The aperture is ovate ; the columella is stout, 

 oblique, and bears a strong fold a little below its insertion ; the parietal 

 wall is glazed by a thin callus ; the outer lip is thick and seems to show 

 indications of spiral cords deep within. 



The type, U.S.N.M. No. 561692, comes from the Pliocene of North 

 St. Petersburg, Fla. It has 9 whorls remaining and measures : Length 

 5,7 mm., diameter 1.5 mm. Another specimen is in the collection of 

 the A.N.S.P. 



The stout form and different spiral sculpture will readily distinguish 

 this species from the other Mormulas, having retractively slanting 

 axial ribs. 



I take pleasure in naming this species for Dr. Henry A. Pilsbry, 

 one of the world's foremost malacologists. 



MORMULA ROBERTSONAE, new species 



Plate 5, figures 3a, b 



Shell elongate-turrited, cream-yellow. The nuclear whorls are 

 decollated in all our specimens. The postnuclear whorls are rather 

 high and flattened. They are marked by strong, retractively slanting 

 axial ribs, which are of the same strength from the summit to the 

 suture. Of these ribs 16 are present upon the first of the remaining 

 whorls and 18 upon each of the rest, except for the last, where they 

 become enfeebled, less regular and less distinct. At irregular intervals 

 some of the ribs become thickened to form a varix. The intercostal 

 spaces are about as wide as the ribs and are crossed by six grooves 



