THE NAUTILUS. 139 



Remarks: Thia species is smaller than the one previously de- 

 scribed. The sides more nearly parallel, the canal more twisted, 

 and in the young we find two strong transverse lines witha fiattened 

 space between. Sometimes they are smooth otherwise and sometimes 

 strongly marked with raised axial lines. 



11. Paludestrina plana n. sp. PI. 8, fig. 3. 



Shell small, acuminate; whorls seven, smooth and rounded, suture 

 deep, aperture oblong-ovate, outer lip slightly expanded; peristome 

 continuous; umbilicus open but minute. 



Length 4 mm. 



Remarks: In some specimens the body whorl is slightly separated 

 from the preceding ones, probably pathologic. In others the outer 

 lip is thickened and a slight callus shows over the inner lip. A few 

 distorted specimens with thickened shell were obtained. 



12. Amnicola saltillensis n. sp. PI. 9, 10, figs. 5-12, 15. 



The extraordinary distortions of nearly all the species of this genus 

 makes any specific determination difl[ioult. Three species are de- 

 scribed; perhaps there should be four. The typical form of this 

 species is shown in figure 5. 



Shell small, surface smooth, whorls five tapering regularly, suture 

 distinct, whorls sometimes slightly shouldered. Body whorl rotund, 

 umbilicus small, aperture pointed slightly above, rounded at base, 

 outer lip slightly thickened. 



Height 2 mm., body whorl 1 mm. in breadth. The greater num- 

 ber of the distorted forms are assigned to this species. 



List of illustrations is as follows: 



No. 5 = normal. 



No. 6 = young shell (may be distinct). 



No. 7 = distorted at apex with body whorl enlarged. 



No. 8 = the distortion begins with the older whorls, younger part 

 is normal. 



No. 9 = a different view of No. 8. 



Nos. 10 and 11 = two views of still another form. 



No. 12 = both the apical and body whorls involved. 



No. 15 = young shell with the apical whorls sunken in. 



13. Amnicoi.a georgiensis n. sp. PI. 9, 10, figs. 4, 4a and 13. 

 Similar to the preceding, not so elevated, with wider umbilicus, 



