254 NEW FOSSIL SHELLS 
FAMILY NERITIDZE. 
GENUS NATICA. 
N. aperta, Pu. 36. Fic. 51. 
N. testa oblique ellipticd, tenut, costulatd, sub-striatd, perforata; spird depressd, ovatd, obtusd, prope apicem levi; 
suluris parvis, tinearibus; anfractibus quatuor, convexis; costulis transversalibus, crebris, planis, quadrangularibus; 
striis longitudinalibus, minutissimis; anfractu ultimo ovato; basi obliqué costulatd; perforatione parvd, angustd; 
apertura maxima, superné sinuatd, inferne ellipticd. ‘ 
Shell obliquely elliptical, thin, costulate, sub-striate, perforate; spire depressed, ovate, obtuse, smooth near the 
apex; sutures small, liner; whorls four, convex; costule numerous, transverse, quadrangular, flat; strie longitudinal, 
very small; last whorl ovate; base obliquely costulate; perforation small, narrow; mouth very large, sinuate above, 
elliptical, below. 
Length .70. Breadth .62 of an inch, 
Remarks.—TVhe costule are small, wider than the spaces between them, and very 
numerous. ‘The longitudinal lines of growth are exceedingly minute; so much so as to 
be invisible to the naked eye. Both ribs and strie become obsolete on the upper whorls, 
so that the two or three nearest the apex are smooth. The mouth is somewhat hunate, 
contracted above and expanded below. The umbilicus is small, and nearly concealed 
by the columella. 
This shell is closely allied to the N. fragilis, Conrad, and’ it is with some hesitation 
that I separate it. I, however, differs in the ribs, the umbilicus, and the shape of the 
mouth. 
N. spHrmruius, Pi. 36. Fic. 52. 
N. testé gleboso-acuminald, obliqua, tenui, levi, politd, imperforatd; spird breviusculd, sub-conicd, acuta; suturis 
parvis, impressis; anfractibus quatuor, sub-convexis; anfractu ultimo rotundato; basi levi; umbilico occulto; callo 
semicirculari, lined impress marginato; apertura semi-ovatd; columella rectd, superne incrassatd. 
Shell globosely acuminate, oblique, thin, smooth, polished, imperforate; spire rather short, sub-conical, acute; su- 
mall, impressed; whorls four, somewhat convex; last whorl rounded; base smooth; umbilicus hidden; callus 
aicircular, margined by an impressed line; mouth, semi-ovate; columella straight, incrassated ahove. 
Length .12. Breadth .11 of an inch. 
Remarks.—This shell is too small and. perfect to be the young of so large a species as 
N. duplicata, which it resembles. Out of twenty or thirty specimens the admeasure- 
ments given above were the largest, the others decreasing to a size scarcely visible with- 
out a microscope. The only other species to which it is allied is the N. percallosa, 
Conrad, but the small size and more elevated spire distinguish it. 
N. CRASSILABRUM, Pi. 36. Fic. 53, 
N. testd transverse ellipticd, depressd, crassd, levi, politd, imperforatd; spird conict, obtusi, valde depressd; suturis 
‘ ; ; 5 > ‘ 
profundis, linearibus; anfractibus quatuor, convexis, superne planulatis; anfractu ultimo rotundato; basi levi; um- 
bilico occulto, parvo; apertura sub-rotunda; labro superne valde incrassato. 
Shell transversely elliptical, depressed, thick, smooth, polished, imperforate; spire conical, obtuse, very much de- 
pressed; sutures deep, linear; whorls four, convex, flattened above; last whorl rounded; base smooth; umbilicus 
hidden, small; mouth sub-rotund; outer lip much thickened above. 
