134 Trans. Acad. Sci. of St. Louis. 
the peripheral carina flattened, duplex to complex, and bearing 
more or less conspicuous nodules, in having the deep parallel- 
sided anal sinus borne centrally on the peripheral carina, as in 
Lophiotoma, and, in having a large closely coiled multispiral 
conically or ogivally pointed embryo, with two or three smooth 
apical, and one to three longitudinally ribbed basal, whorls. 
The canal is moderately long, and straight, or nearlyso. The 
American fossil species known to me may be identified by the 
following characters : — 
Costuliform denticulations of the more strongly elevated peripheral carina, 
short, varying in length from scarcely a fourth to a sixth or seventh 
part of the entire length of the WHOTrIS....sseesccseececcerecereeres 2 
Costulations longer, the peripheral band much broader and generally less 
strongly elevated, about a third as wide as the length of the whorls, 
the costules usually becoming gradually less distinct on the larger 
whorls......- aleve alesielole's \ehevsloielc)oravisle wien slalelatnvele\s cletelelato\sreneoieleheistelakeinta Sando Lt 
2— Denticulations remaining equally well developed and conspicuous 
throughout the life of the shell or virtually SO....se.+-eeeeeeeseeeee D 
Denticulations only distinct on the young body whorls, becoming gradu - 
ally more ill defined and obsolete or subobsolete on the larger whorls; 
species rather larger in SiZC. cece seve voce cece coerce recececcsseerse 1 
3 — Denticulations in the form of small longitudinal costules from one of 
the two peripheral carinae to the other, crossing the intervening feeble 
depression with but partial interruption..... severe ce ereeeeeee rene & 
Denticulations feeble, ia thé form of compressed nodes of the individual 
peripheral carinae and much broader in a spiral direction than long.. 11 
4—Fasciolar surface below the subsutural carina deeply concave, then 
rapidly expanding to the strongly elevated peripheral carinae........ 5 
Fasciolar surface below the subsutural carinule very feebly concave, but 
obliquely and only moderately rapidly expanding to the less elevated 
peripheral Carinae........e.seeee slisiatelaioleteie) wietelelora Geta} vetereley sletoieuelerstalterereanal 
5— Form stout, the apex of the beak distinctly reflexed; subsutural con- 
cavity with only about two fine revolving threads which are situated 
at the middle of the concavity; embryo rather large and well developed, 
higher than wide, with two or three very small smooth whorls at the 
summit, followed by three Jarger whorls which are conspicuously cos- 
tulose, the riblets of the lowest whorl coarser and generally more 
widely spaced than the others. Red Bluff Eocene.........amica Csy. 
Form slender, the beak not reflexed at apex; concave surface below the 
subsutural carina with a greater number of fine spiral threads, about 
three on the largest whorl of genitiva, numerous in rotaedens; embryo 
smaller but almost similarly formed and sculptured.........-- Soodbos (& 
6 — Peripheral double carina at the middle of the whorls, the denticulations 
rather fine; form very slender, the aperture and canal combined abouta 
third of the total length. Upper Vicksburg Oligocene.. -rotaedens Con. 
