302 PHASIANELLIDA. 
somewhat embracing above, and each hiding all the preceding 
ones below; aperture wider than high ; peristome not continuous ; 
labrum simple, projecting forward above; labium a little sinuous 
and slightly spreading in the more or less impressed umbilical 
region. 
P1ronELius, Montfort. 
Syn.—Ptychomphalus, Agassiz. Lewisiella, Stolicz. 
Disir.—Lias, Cretaceous; Europe. P. archiacianus, d’Orb. 
(xxix, 2)... 2. conicus, d'Orb, (xxix,as). 
Shell depressed or conic, whorls generally rounded, the base 
with a very strong shining callus; lip simple, sharp. 
CrossostoMa, Morris and Lycett. 
Distr.—2 sp.  Oolite; England. C. Prattii, Morris and 
Lycett (Ixxix, 4). 
Shell thick, depressed turbinated, without umbilicus ; aper- 
ture subrotund, entire; outer lip smooth; columella toothed 
when young, tooth concealed by callus in the adult. 
TROCHOPSIS, Gemmellaro, 1878. Shell top-shaped, thick, shining, 
imperforate ; outer lip with four inferior tuberculate spiral ribs ; 
inner lip curved, sharply defined by a furrow. C. Moroi,Gemm. 
Liassic. 
PTEROCHEILOS, Moore. 
Distr.—Pt. primus (1xxix,5),  Liassic ; England. 
Very thick, small, with the general contour angulated or 
rhomboidal, smooth, spire short, periphery of last whorl cari- 
nated, the carina terminating in a wing-like projection of the 
outer lip; aperture with a thick, circular peristome, columella 
thick, folded, subumbilicated, greatly extending beyond the 
peristome, and possessing a wide but shallow sulcus towards 
its base. 
PLEURATELLA, Moore, 1867. 
Distr.—P. prima, Moore. Lias; Europe. 
Shell small, thick, smooth; spire much depressed ; whorls 
4-5, rapidly enlarging; last whorl very large, rounded ; aperture 
round or oval; inner lip straight, with thick lengthened colu- 
mella, having an umbilicus-like groove. 
Famity PHASIANELUID AS. 
Shell bulimiform, smooth, polished, richly ornamented with 
bright colors, without epidermis. Operculum oval, calcareous. 
Animal with long ciliated tentacles; head-lobes pectinated, 
wanting in the minute species; neck-lobes fringed; sides orna- 
mented with three cirri; branchial plume long, partly free ; foot 
rounded in front, pointed behind. 
Distinguished from the Turbinidw by the form of the shell, 
