SHELL. 
Cjpraea. A convex, univalve shell, the 
edges turned inwards ; the opening long 
and narrow, and toothed on each side. 
The shells of this genus are so distinctly 
characterized as to have escaped that con- 
fusion which has taken place in many other 
genera. 
Conus. A conical, convoluted univalve ; 
the opening of the length of the shell, linear, 
without teeth, and hollowed out at the top ; 
the coluniella smooth. The generic cha- 
racters are here so determinate, as not to 
have left any opportunity for changing the 
acceptation of this genus, as established by 
Linnaeus. 
Vermicularia. A tubular shell, twisted 
in an irregular spiral, in general adhering to 
some body ; and furnished with an opercu- 
lated opening. The shells with which La- 
marck has formed this genus, were blended 
by Linneeus with the Serpulae ; but the ani- 
nsals which inhabit these shells are very dif- 
ferent from the Terebrellie, which are the 
only inhabitants of the true Serpulae. 
Silicaria. A tubular shell, spirally convo- 
luted, and laterally divided through its 
whole length by a narrow fissure; the 
mouth roundish. Linnaeus himself consi- 
ders it as doubtful whether the shell which 
forms this genus (Serpula anguina) should be 
placed under the genus Serpula, or not ; 
but Bruguiere, Lamarck, and Daudin, have 
thought itnece.ssary to establish for it this 
new genus. 
Penicellus. A long tubular copical shell, 
the superior extremity closed by a disc, 
beset with numerous short tubes, and sur- 
rounded by a projecting coronet ; the infe- 
rior extremity having been fixed to some 
solid body, Linnaeus had doubted whether 
the .shell, of which Bruguiere has formed 
this genus, ought not to be placed under 
the genus Teredo, rather than under that 
of Serpula, where, however, he left it. 
Nautilus. A spiral and nearly discoidal 
shell, the last turn of which envelopes the 
rest, and the sides of which are smooth: 
numerous chambers formed by transverse 
smooth septa, perforated by a tube. This 
^enus is divided by Lamarck into three. 
1. Nautilus, 2. Spirula, 3. Orthocera. 
Orbulites. A spiral, and nearly discoidal 
shell, the last spire enveloping the rest ; the 
sides articulated by winding sutures ; the 
transverse septa? being pierced by a margi- 
nal tube. The shells which Lamarck has 
assumed for this genus have been hitherto 
confounded with the Ammonites: they are 
only known as fossils and as casts. 
Ammonites. A discoidal spiral shell, the 
turns contiguous and all visible, the sides 
articulated by foliated sutures, and the 
transverse septic terminating in winding 
processes, and pierced by a marginal tube. 
These, like the shells of the preceding ge- 
nus are only with certainty known to exist 
as fossils. 
Planulites. A discoidal spiral shell, with 
contiguous and visible turns, with smooth 
sides, and transverse septae, not foliated. 
These shells are supposed to bear the same 
relationship to the Ammonites as the Nautili 
do to the Ammonites ; but the difference 
between them and the Ammonites is so lit- 
tle as must often be with difficulty disco- 
verable. 
. Camerina. A shell with a single valve, 
without any external spire, the internal 
part divided into numerous chambers by 
imperforated septa. This genus was formed 
by Bruguiere for the reception of the fossil 
shells long known as Lapides lenticulares 
and Nummulites. 
Ilotalites. A depressed orbicular, discoi- 
dal chambered shell, smooth on the upper, 
radiated on the under side, with tubercular 
and unequal points in the centre ; the edge 
carinated, and having a small trigonal mar- 
ginal opening. The fossil shell on which 
this genus was formed, is figured and de- 
scribed by Guettard in his Memoirs on 
Fossils. 
Tiiriilites. A spiral turbinated shell, with 
contiguous and visible turns, the sides arti- 
culated by winding sutures ; transverse 
pierced septa, with foliated terminations; 
the opening round. The shells belonging 
to this genus are all fossil, and even the 
fragments of their casts are very rare. The 
characters of the shells of this genus are 
very striking, their internal structure being 
similar to that of the Ammpnites, whilst 
they possess a turriculated or wreathed 
form. 
Baculites. A straight cylindrical and ra- 
ther conical shell; the sides articulated by 
winding sutures ; the transverse septa ter- 
minating in foliaceous forms. This genus is 
founded on a fossil shell described by Fau- 
jas St. Fond in his Natural History of St. 
Peter’s Mountain near Maestricht, and 
which he considers as a straight Ammo- 
nite. 
Spirula. A shell partially or completely 
in a discoidal spire; the turns separate, and 
the last extending into a straight line ; 
transverse smooth septa, pierced by a tube , 
the opening round. This genus comprises 
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