SHELL. 
tftnt of the sea, for swimming, instead of 
'that for crawling, with which the Helices 
are provided. It is nearly globular, and al- 
most diaphanous ; the opening is nearly 
triangular, with an angular sinus at the right 
«dge. 
Turritella. This genus was formed by 
Lamarck, for the reception of those shells 
which Linnmus had placed in the last sec- 
tion of his genus Turbo, as Towers ; and 
which Dargenville and Favanne had consi- 
dered as screws. The characters of the 
genus are, a turriculated shell ; the opening 
round, whole, but having a sinus at the 
right edge. 
Cyclostoma. Tliis genus was formed by 
Lamarck for the reception of the Wentle- 
trap, and other shells of the same character. 
The propriety of thus forming a new genus 
is rendered evident by the, doubts which 
had arisen respecting the placing of it in 
any old genus. Linneeus having considered 
it a Turbo ; Rumphius, a Buccinum ; Dar- 
genville, a Screw; and Davila, Gualteri, 
Guettard, and Favanne, merely a Tube, 
from its not possessing a columella, which 
they considered as essential in a univalve 
shell. The shells of this genus ditfer in 
their forms ; their openings are nearly round, 
and their sides connected circularly. The 
shell is formed of seven spires, separated 
by a void space ; with ten or twelve longi- 
tudinal ribs, which uniting, form a rim 
round the lip. These ribs externally supply 
the place of a columella. 
Bulimns. A globular, oval, or turricu- 
lated shell, the opening of which is entire, 
not grooved at the base, and always longer 
than wide. This genus of Bruguiere com- 
prises some of the shells considered by Lin- 
nseus as Helices and Bullae ; and the genera 
Auricula, Pyramidella, Melania, Lymnsea, 
Agathina, Maillot, and Bulima, of Lamarck. 
The essential character distinguishing this 
genus from Helix is the opening being lon- 
ger than it is wide. 
Turbo. A conoidal or turriculated shell; 
the opening entire, round, without any 
tooth; the edges disjoined on the superior 
part. Several shells which were reckoner! 
by Linnmus of this genus have been remov- 
ed from it by Bruguiere, and placed under 
his genus Bulima, and others have been 
taken from it by Lamarck, and disposed 
under the genera Cyclostoma and Tur- 
ritella. 
Trochus. A conical univalve shell; the 
opening almost always quadrangular, flat- 
tened transversely ; the columella oblique. 
Lamarck has divided tliis genus into four: 
1. Trochus. 2. Solarium, witlr an open, um- 
bilicus, or crenulated opening on the inside 
of the spiral turnings, as in the Trochus per- 
spectivus. S.Monodenta. The opening round- 
ed, and furnished with a tooth formed by the 
truncated and projecting base of the columel- 
la, as in Trochus labio, Linnmus. 4. Pyrami- 
della; the columella projecting, perforated 
at its base, and possessing three transverse 
folds, as in Trochus dolabratus, Linnaeus. 
Cerithium. A univalve turriculated shell, 
the opening terminated at its base by a 
short, narrow canal, either suddenly turning 
backwards or truncated, but never grooved 
out. In this genus of Bruguiere are com- 
prehended several shells from the genera 
Trochus, Strombus, and Murex of Linnaeus. 
The shells differ from those|of Murex by their 
turriculated form ; and from the screws, in 
not having the groove at the base of the 
canal. 
Pyrula. A subpyriform shell, canalicu- 
lated at its base ; without any projections, 
and having the belly part nearer to its sum- 
mit than to its base ; the spire short ; the 
columella smooth ; the right edge without a 
groove. Lamarck founding the distinction 
on the situation of the bellied part of the 
shell, and on the greater or less length of 
the spire, has formed two new genera ; one 
with those shells possessing this character 
of the genus Bulla, and the other of the 
genus Murex, calling the former Pyrula 
and the latter Fusus. 
Murex. An oval or elongated univalve 
shell, generally foliated, plaited, spinous, or 
tuberculated ; the opening always prolonged 
into a canal, running straight, or turning 
directly backwards, and always entire. In 
the earlier stages of their growth it is diffi- 
cult to separate the Murices from the 
Strombi. Lamarck divides this genus of 
Linnmus into five genera. 1. Murex, with 
tuberculated or spinous projections, and 
channelled at the base, as M. ramosus. 
2. Fusus ; fusiform, without projections, 
with the bellied part either equally distant, 
from the extremities or nearest to the base ; 
spire elongated; columella smooth; right 
edge without groove, as M. coins. 3. Fas- 
ciolaria; nearly fusiform; no projections; 
with two or three very oblique folds on the 
columella ; and channelled at the base, as in 
M. tulipa. 4. Pleurotoma : fusiform or 
turriculated,without projections, and having 
a groove, or sinus, near the summit of the 
right edge, as in M. babylonicus. 5. Ce- 
rithium, already described. 
