1903.] NATURAL SCIENCES OF PHILADELPHIA. 277 



4 — -Peripheral carina at or above the middle of the wliorls ; concave f asciolar sur- 

 face simple or with one or two fine simple revolving threads 5 



Peripheral carina below the middle of the whorls; beak well defined and rapidly 

 acuminate ; f asciolar surface with a conspicuously beaded thread ; embryo 

 with two or tliree smooth and about two costulate whorls; body whorls 

 three or four in number 7 



5 — Base of the shell distinctly rostrate; body whorls about four in number. 

 Form stout, the spire whorls short, about three times as wide as long, with 

 a subduplex subsutural collar and three other single carinre, the fasciolar 

 surface with two fine revolving threads; beak short and broad; lines of growth 

 strongly marked; embryo well developed as usual, higher than wide, ovulate 

 at tip, with three smooth and two costulate whorls. Length 5.7 mm., 

 width 2.3 mm. Lignitic Eocene. Wood's Bluff horizon, rostrahda, n. sp. 



Base of the shell angularly acuminate, not at all rostrate; body wliorls variable, 

 but never exceeding four as far as knowni 6 



6 — Embryo as wide as high, obtusely oval at tip, with three smooth and two 

 costulate whorls ; subsequent whorls four in number, each with one subsutural 

 and three other equal carinte; fasciolar surface without a revolving thread. 

 Length 5.6 mm., width 2.25 mm. Lower Claiborne Eocene. St. Maurice, 

 La robustula, n. sp. 



Embryo acutely conical, scarcely higher than wide, with three smooth and one 

 costulate whorls ; subsequent whorls not more than two in number in any of 

 the three type specimens at hand, similar to those of robustula, but much 

 more slender. Length 2.3 mm., width 1 mm. Lower Claiborne Eocene. 

 St. Maurice, La minutissima, n. sp. 



Emljryo larger and much more complex, evenly conical, as wide as high, with 

 two small smooth whorls and three finely and closely costulate, the latter 

 strongly convex near their basal margins; form rather stout; whorls two 

 in number in specimens at hand, the fasciolar surface without a revolving 

 thread. Length 3.9 mm., width L5 mm. Red Bhiff Eocene. 



[Pleurotoma] infans Meyer 



Embryo nearly one-half higher than wide, subcylindrical, rapidly pointed at 

 tip, with three smooth and nearly three coarsely costulate whorls, the latter 

 strongly and more medially convex; subsequent whorls not exceeding four 

 in number, the fasciolar surface with a fine revolving thread ; shell much more 

 slender and elongate than in infcms. Length of embryo alone L4 mm., width 

 .8 mm. Upper Vicksburg Oligocene vicksburgella, n. sp. 



7 — Beaded thread below the middle of the fasciolar surface, a finer simple thread 

 between it and the subsutural carinule; granulations of the beaded thread 

 fine but distinct. Length of a specimen of 3.5 body whorls 6.7 mm., widtl^ 

 2.6 mm. Lower Claiborne Eocene. St. Maurice, La. 



[Pleurotoma] lerchi Vgn 



8 — Spire more rapidly narrowed toward apex, the embryo very small, of three 

 or four whorls, the lowermost apparently costulate; body whorls five to six 

 in number, each with subsutural and submedian coarse equal carinse and 

 a third, finer and less conspicuous, between the latter and the base ; concave 

 fasciolar surface between the coarse carina with a fine median revolving 

 thread; lines of growth well marked as usual; columella subumbilicate as a 



