586 PROCEEDINGS OF THE ACADEMY OF LDeC, 



A. Whorls with transverse (axial) ribs and microscopic spiral strise. 

 a. Length of shell, 10 mm. or more. 



b. Labium separated by a groove or space from the penul- 

 timate whorl. 

 1. Labrum not separated from labium by a sinus, well 

 produced obliquely and downward; size, 16x3.8 

 mm procera C. B. Ad. 



bb. Labium not separated from penultimate whorl. 



c. 2. Labium expanded convexly, not much produced be- 

 low; size, 11 x 3.5 mm minor C. B. Ad. 



cc. Labrum produced below. 



3. Linguiform part of labrum much produced, subacute, 



40 ribs per whorl; size, 14 x 3.3 mm., 



gracilis C. B. Ad. 



4. Linguiform part excessively produced, very narrow 



and subacute, 26-30 ribs per whorl; size, 12 x 3.2 

 mm. typica C. B. Ad. 



ao. Length of shell less than 10 mm. 



d. Labium detached from the penultimate whorl. 

 e. Labium widely detached from the penultimate 

 whorl. 



5. Labium very widely detached from the penul- 



timate whorl, linguiform part obtuse and 

 produced laterally, 40 arcuate ribs per 

 whorl ; size, 9.4 x 3 mm. costulosa C. B. Ad. 



6. Labium rather widely detached, linguiform 



part on lower half of labrum and scarcely 

 produced; ribs, 35 per whorl; size, 6f x 1.6 



mm. exilis C. B. Ad. 



ee. Labium moderately or only slightly detached 

 from the penultimate whorl. 



7. Labrum separated from labium by a keyhole 



sinus, labium distinctly detached from 

 the penultimate whorl; size, 5| x 1.2 mm., 



sinuosa Chitty. 



8. Entire end of last whorl a little detached 



from the penultimate whorl and angular 

 above, lip sharp, labium reflected (oppo- 

 site the penultimate whorl); labrum 

 (otherwise) scarcely reflected; size, 7.5 x 

 1.7 mm. beardsleyana C. B. Ad. 



9. Labium slightly detached, prominent, thick- 



ened; labrum but little produced below, 

 moderately thickened and reflexed, 



elegans C. B. Ad. 



10. Labium slightly detached and separated from 

 labrum by a slight sinus; ribs widely 

 spread, 8 to a whorl, excessively elevated, 



