NO. 2 PYRAMIDELLID MOLLUSKS — BARTSCH 69 



This species is nearest related to Chrysallida mansfieldi (p. 6y), 

 from which its more slender outline will easily distinguish it. 



It is named for F. Stearns Macneil, of the United States Geological 

 Survey, who has been devoting much time to Tertiary paleontology. 



CHRYSALLIDA SIMPSONI, new species 

 Plate IS, figure 11 



Shell large, elongate-conic, cream-yellow. The nucleus consists of 

 about 2 whorls, which form a depressed helicoid spire whose axis is 

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

 which the nucleus is deeply immersed, showing only the tilted edge 

 of the last turn. The postnuclear whorls are weakly rounded and 

 marked by moderately strong, vertical axial ribs which are of the 

 same strength from the summit to the fifth spiral cord. Of these ribs 

 12 are present upon the second, 14 upon the third, 16 upon the fourth, 

 18 upon the fifth, 22 upon the sixth, and 25 upon the last whorl. The 

 intercostal spaces are much narrower than the axial ribs. The spiral 

 sculpture consists of five cords between the summit and the periphery, 

 of which the posterior 4 are equal and equally spaced ; the fifth cord 

 near the periphery is a little weaker with less strongly developed 

 nodules. The junction of the spiral cords, which almost equal the 

 axial ribs in strength, with the ribs forms strongly elevated hemi- 

 spherical tubercles, while the spaces enclosed between them are deep, 

 round pits. The suture is strongly impressed and rendered wavy by 

 the tubercles at the summit. The periphery is marked by a strong 

 spiral cord. The base is well rounded and marked by seven subequal 

 spiral cords and numerous slender axial threads. The aperture is 

 elongate-oval ; the columella is oblique and bears a strong fold at its 

 insertion ; the parietal wall is glazed by a thin callus ; the outer lip is 

 gently curved and rendered sinuous by the external cords. 



The type, U.S.N.M. No. 561707, comes from the Pliocene of North 

 St. Petersburg, Fla. It has 7.5 postnuclear whorls and measures : 

 Length 5.0 mm., diameter 1.3. U.S.N.M. No. 561708 contains 

 another specimen from the same source, and two more are in the 

 collection of the A.N.S.P. 



The strongly developed sculpture will readily differentiate this 

 species from the other two that have five spiral cords. 



I take pleasure in naming this species for Charles T. Simpson, who 

 was for many years assistant curator of the division of mollusks at 

 the United States National Museum. He is the author of the Manual 

 on American Fresh Water Mussels. His immense collection of 

 mollusks is at the University of Miami. 



