FROM THE TERTIARY OF VIRGINIA. 273 
sides a smaller one near the superior suture. ‘They are perfectly quadrangular, having 
perpendicular sides and a flat top. When they cross the sulcations, they appear slightly 
nodulous. The spaces between them are about equal to them in width. Those on the 
base are closer and more acute. About three whorls of the apex are perfectly smooth. 
This little species can be readily distinguished from its congeners by the peculiar 
shape of its transverse ribs. 
GENUS NASSA. 
N. mpressa, Pu. 37. Fie. 101. 
N. testé eclongato-ovatd, crassd, imperforatd, costatd, striata; spird attenuata, comcd, obtusd, prope apicem levi et politd; 
suturis impressis, flexuosis; anfractibus septem, convexis, ad sutwram superiorem angulatis; costis longitudinalibus, latis, ro- 
tundatis; striis transversis, parvis, flecuosis; anfractu ultimo rotundato; basi striatd; aperturd sub-ellipticd; canale brevi, 
obliquo; labro intus minute dentato. 
Shell elongately ovate, thick, imperforate, costate, striate; spire attenuate, conical, obtuse, smooth and polished 
Barely ) ’ D ? ’ ) ) ) ] 
near the apex; sutures impressed, flexuose; whorls seven, convex, angular near the upper suture; costa longitudinal 
wide, rounded; strie transverse, flexuose, small; last whorl rounded; base striate; mouth sub-elliptical; canal short, 
oblique; outer lip minutely dentate within, 
Length .20. Breadth .11 of an inch. 
Remarks.—The transverse strie are small and abrupt; they cross the ribs. There is 
one rather deeper than the rest on the angle of the whorls, above this is a very small one, 
and between this and the suture the surface is smooth. ‘The costa are very large and 
wide, generally rounded, but occasionally somewhat angular. ‘The three first whorls of 
the spire are smooth. ‘There are two or three teeth of various sizes on the inside of the 
outer lip. 
This little shell differs in various respects from all of our other species of Nassa. It 
is more elevated than is usual with the genus. ‘The strie are fewer and the coste larger 
than in the recent N. alba, Say, to which, in sculpture, it bears some resemblance. 
FAMILY COLUMELLID/. 
GENUS MARGINELLA. 
M. conurtus, Pu. 87. Fie. 102. 
M. testdé obovatd, conoidali, crassa, levi, politd; spird conicd, obtusd; suturis sub-obsoletis; anfractibus tribus, planis; an- 
fractw ultimo rotundato; basi levi; apertura longd, arctatissima; columella inferné plicis tribus; labro incrassato, rotundato, 
levi. 
Shell obovate, conoidal, thick, smooth, polished; spire conical, obtuse; sutures nearly obsolete; whorls three, flat; 
last whorl rounded; base smooth; mouth long, very narrow; columella with three folds near the base; outer lip thiek- 
ened, rounded, smooth. 
Length .12. Breadth .08 of an inch. - 
Remarks.—The whorls of the spire are very small, and the sutures almost obliterated, 
so that they can scarcely be seen except on a perpendicular view. The folds on the 
columella are very near the base, and quite small. The shape of the mouth is almost 
linear. 
This shell is more nearly allied to the M. incurva, Lea, than to any other, but differs 
in the number of the folds on the columella, and the incrassation of the outer lip. 
VOL. IX.—72 
