264 NEW FOSSIL SHELLS 
Remarks.—The carina on the last whorl is very large. There is a corresponding 
depression in the interior of the mouth. Occasionally, there is an angulated line near 
the suture of the last whorl, but this is not a constant character. ‘The carina is rather 
nearer the apex than the base of the shell. ‘The substance is exceedingly thin, and has 
somewhat the appearance of ivory. On a front view, the general outline of the shell has 
a remarkably rhomboidal shape. 
I know of no species of Rotella, except the following, which resembles this beautiful 
little shell. 
R. LenticuLaris, Pu. 36. Fie. 79. 
R. testd lenticulari, depressi, tenui, levi, politd; spird brevissimd, sub-ovatd, obiusd; suluris parvis, linearibus; 
anfractibus quatuor, convemis; anfractu ultimo angulato; basi levi; callo parvo; apertura sub-rotundd; columella latd, 
curvata. 
Shell lenticular, depressed, thin, smooth, polished; spire very short, sub-ovate, obtuse; sutures small, linear ; 
whorls four, convex; last whorl angulate; base smooth; callus small; mouth sub-rotund; columella broad, curved. 
Length .04. Breadth .09 of an inch. 
Remarks.—The angle on the last whorl is very variable. It sometimes amounts 
almost to a carina. The mouth is nearly round. The callus is slightly depressed 
below the surrounding surface. 
This shell is, in part, allied to both the preceding species, but differs in the number 
of whorls, shape of the columella and spire, and the angle on the last whorl. ‘They 
also differ much in thickness, 
R. umpiiicata, Pu. 36. Fie. 80. 
R. tesid orbiculari, valde depressd, crassd, levi, politd; spird umbilicatd; anfractibus occultis; anfractu ultimo ro- 
tundato, spiram tegente, ad suturam superiorem lined parva impressé transversd; basi levi; callo magno, tenui, medio 
depresso; aperturd rotunda; columella latissimd, subsulcatda. 
Shell orbicular, very much depressed, thick, smooth, polished; spire umbilicate ; whorls concealed; last whorl 
rounded, covering the spire, with a small impressed. transverse line near the superior suture; base smooth; callus 
large, thin, depressed in the middle; mouth rotund; columella very wide, sub-sulcate. 
Length .05, Breadth .10 of an inch. 
Remarks.—The columella has a shallow groove in its centre. The mouth is almost 
round. 
This little shell, in general outline, is not unlike the R, nana, Lea, but the peculiar 
umbilicated spire will at once distinguish them. 
This genus is quite rare in a fossil state. I believe that but one, the R. suturalis, has 
been found in the Tertiary beds of Europe. In this country the species appear to be 
more numerous. 
GENUS TROCHUS. 
T. ARMILLUS, Pu. 37. Fie. 81. 
T. testa conicd, elevaté, crassiusculd, imperforatd, costatd, striatd; spird conicd, acuminata; suturis minimis; an- 
fractibus quinque, planis; costis transversis, tribus, noduliferis, alternantibus striis minimis; anfractu ultimo acuté 
angulato, carinato; basi valde planulato, striis magnis et parvis; apertura quadrilateral:. 
