136 CONCHOLOGY. 
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minates the shell; an operculum. This genus is distinguished 
from the Strombus by having a sinus in the lower part of the right - 
margin contiguous to the canal. Inhabits the European seas 
four living species. Three fossil. 
Rostellaria curvirostris. Rostellaria pespelicani. 
R. rectirostris. R. cancellata. 
2. Genus Pieroceras. Pl. XII. 
Animal. See Strombus, below. 
Shell. Oblong-ovate ; canal elongated, attennated and often 
closed ; right margin dilating by age into an expanded digitated 
wing, attached to and covering a short spire with a sinus in the 
lower part not contiguous to the body. Distinguished from the 
Strombus by not having the canal at the base shortened or trun- 
cated, and from the Rostellaria by having the sinus of the right 
margin distant from the body. Found in the Equatorial seas. 
Seven species. Five fossil. 
Pteroceras truncata. Pteroceras chiragra. 
P. lambio. P. millepeda. 
P. scorpio. P. pseudoscorpia. 
P. aurantia. 
3. Genus Strombus. Pl. XII. 
Animal. Spiral; the foot rather wide anteriorly, compressed 
posteriorly ; mantle thin, forming a prolonged fold anteriorly, 
whence issues a sort of canal; head very distinct; mouth a ver- 
tical slit at the extremity of a proboscis, provided in the inferior 
median line with a lingual band having prickles flexed posteri- 
orly ; tentacular appendages cylindrical, thick, and long, with the 
eyes at their extremity. 
Shell. Thick, subinvolute, dilated in the middle, terminating 
in a cone anteriorly and posteriorly ; aperture very long and 
narrow ; terminated anteriorly by a canal more or less elongated 
and flexed; edges parallel, the external dilating with age, pre- 
senting posteriorly a gutter at its point of attachment with the 
spire, and, anteriorly, a sinus behind the canal, through which 
the head of the animal passes; operculum horny, long, and 
