136 Trans. Acad. Sci. of St. Louis. 



than half the length of the shell. Length of a specimen having 4 body 

 whorls, 7 mm. ; width, 2.7 mm. Lower Claiborne Eocene of St. Maurice, 

 La parvidens n. sp. 



11 — Spire elongate, gradually and evenly acuminate, about twice as long as 



the aperture and canal combined; beak gradually acuminate and straight 

 from the abrupt conti^action below the convexity of the body whorl; 

 embryo of the Gemmula type, well developed, of two or three small smooth 

 whorls followed by about three covered with arcuate riblets ; spire whorls 

 each with a strong subtumid subsutural collar which is fully as large and 

 prominent as the obtusely crenulate and obscurely double, generally nar- 

 row and feebly elevated peripheral carina, the latter distinctly below the 

 middle; space below thiscarina with a single spiral carinule; space above 

 it to the subsutural collar, broadly, evenly and rather feebly concave, 

 with numerous very fine spiral threads; peripheral crenulations of the 

 body whorl apparently rather less distinct; they become constantly 

 longer in a spiral sense from one whorl to the next below. Length of a 

 specimen having 6 body whorls, 14 mm.; width, 3.9 mm. Lower Clai- 

 borne Eocene of Lisbon, Ala lancea n. sp. 



12 — Crenulate periphery at, or only slightly below, the middle 13 



Crenulate periphery at, or extremely near, the lower or anterior margin of 



the spire whorls 14 



13 — Crenulations of the periphery fine, apparently not more than a seventh 



or eighth as long as the whorl, becoming obsolete on the seventh or 

 eighth body whorl; subsutural collar apparently present on the crenu- 

 late younger whorls; embryo imperfect in the types. Length of a 

 specimen of about 10 body whorls, 48 mm. Claiborne (ferruginous 



sand) alternata Con. 



Crenulations coarse, becoming on the sixth body whorl large, low, tumes- 

 cent rounded elevations, with no distinct principal carinae, the entire 

 surface having rather close-set and equal fine spiral carinules; on the 

 upper whorl the crenulations are more abruptly formed and are crossed 

 by about three rather coarser lines, but the periphery nowhere has 

 the abruptly elevated form seen in rotaedens and allies; the periphery is 

 distinctly below the middle of the whorl and not at the middle as it 

 seems to be in alternata, and the crenulations are nearly a fourth as long 

 as the whorl, about 18 in number; upper whorls with a distinct subsu- 

 tural collar which disappears completely on the larger whorls; body 

 whorl below the posterior end of the aperture having rather coarse lines 

 separated by about three smaller close-set threads. Length of a 

 specimen having 6 body whorls about 19 mm.; width, 5.6 mm. Lower 

 Claiborne Eocene of St. Maurice, La , . . obsolescent n. sp. 



14 — Shell moderately stout, the spire gradually, evenly acuminate and but 



little longer than the aperture and canal combined; embryo much higher 

 than wide, with numerous riblets as usual; spire whorls evenly sculp- 

 tured throughout with coarser and single finer intermediate spiral lines, 

 not interrupted in longitudinal succession by the obtusely and gradually 

 elevated periphery which bears obtuse crenulations, the latter disap- 

 pearing altogether on about the seventh whorl; surface broadly, feebly 

 concave from the subbasal periphery to the suture above, the latter 

 having no trace of subsutural collar even on the nepionic whorls. 



