MOLLUSCA. 347 
Mollusca. thus defined by the last mentioned author: “ Testa unival- 26. Trocuus. This is a very natural genus in the Lin- Mollusca. 
>’ vis, ovata vel elongata. Apertura oblonga, basi emargina- nean system, and has undergone few alterations in the —\— 
ta, nudata, canali nullo. Collumella convexa plana.” 
Bruguiere separated the genus Cassis, in which the 
opening is oblong and denticulated on the right side, with 
a short canal towards the back of the shell. The right 
margin has a callous border. The Buceinum cornutum of 
Linneus is the type of the species. 
The genus TEREBRA was likewise formed by the same 
author. It is remarkable for its turreted form, the spire 
being at least twice as long as the mouth, and the pillar at 
the base twisted. 
In the genus Nassa the groove in which the mouth ter- 
minates is reflected as in Cassis, but the left edge of the 
mouth is callous, and forms upon the pillar a transverse fold. 
The Purrvr is readily distinguished from the Buccinum 
and Murex, with which it has often been associated by its 
naked compressed pillar, ending in a point at the base. 
The genus Dox1uw is distinguished by its bellied forms 
and transverse rings, together with the margin on the right 
side being denticulated its whole length. 
The genus Harpa is well known, and is distinguished by 
its sharp parallel longitudinal ribs. The pillar is smooth 
and pointed at the base. 
In the genus Esurnea, the shell is smooth, and the pil- 
lar umbilicated and subcanaliculated at the base. The 
buccinum glabratum is the type of the genus. 
24. Srromsvs. This Linnean genus is now converted 
into a family, distinguished by the right margin changing 
its form with age, and having towards the base an inden- 
ture or sinus. It contains four genera, strombus, rostel- 
laria, pterocera, and hippocrenis. 
In the genus Srrompvs, the canal is short, the right 
margin is simple, and ends in a sinus. The S. pugils of 
Linnzus is the type of this genus. 
In the RosteLxarta the canal is produced into a long 
beak, the right edge of the mouth is entire, and rests above 
on the spire, and is sometimes decurrent. The sinus is con- 
tiguous to the canal. The &. cornuta of Mart. (Conch. iv. 
tab. 158. f. 1495,) is the type of the species. 
In the Prerocera the canal is also lengthened, but the 
right margin is dilated and digitated with a sinus near the 
base. The strombus pes-pelicani of our shores is of this 
genus. 
25. Murex. The modern genus of this name is thus de- 
fed by Lamark: “Testa univalvis, ovata vel oblonga ; 
basi caniculata ; suturis varicoso-tumudis, sub asperis, lon- 
gitudinalibus, et persistentibus.” In consequence of this 
restriction, the following genera, among others, have been 
instituted. 
In the genus Fascronartra, the spires are destitute of 
those longitudinal ribs which the murices always exhibit, 
while the pillar is furnished with two or three oblique folds. 
The murex tulipa of Linneus is the type of this genus. 
The shell of the genus Fusus is lengthened, generally 
fusiform, destitute of longitudinal ribs, and bellied in the 
middle or lower part with a smooth pillar and lengthened 
canal. The /’.longicauda, (Lister, tab. 918, f. 11. A.) is the 
type. 
The Prevrotoma is distinguished from the preceding 
by 2 sinus or groove, which appears on the margin of the 
right edge of the mouth, near itssummit. It is represented 
by the M. Babylonicus of Linnzus. 
The genus Cravatuua differs from the former, in pos- 
sessing a short canal, and ought never to have been separ- 
ated. 
In the genus Cerrrurum, the mouth is oblique, termi- 
nating below in a short truncated or recurved canal, and 
having at the upper part a gutter more or less produced. 
The Lympanotonos asper of Mart. (Conch. 4. p. 314. Tab. 
156. f. 1473,) is the type of the genus. 
hands of modern conchologists. The T.perspectivus has 
given rise to a new and very obvious genus, termed Soua- 
RIUM, characterized by the internal spiral edge of the um- 
bilicus being crenulated. Another species, the J. /abio, is 
the type of the genus Monopon', which contains shells 
of an oval form, with a rounded mouth, furnished with a 
tooth, formed by the truncated projecting base of the pil- 
lar: the two margins are separated. The turreted trochi 
of Linnzus constitute the genus PyRAMIDELLA. 
The T. terrestris of British writers is so imperfectly de- 
scribed and figured, that it is impossible to assign it a place 
in the system. It is nearly allied to the helix. 
27. Turso. This very extensive genus has been greatly 
dismembered by modern conchologists, in consequence of 
Lamark having restricted the character in the following 
terms: “ Testa univalvis, conoidea vel subturrita. Aper- 
tura integra rotundata, edentula; marginibus superne sem- 
per disjunctis ; columella basi planulata.” Our T. littoreus 
is now considered as constituting the genus Lirrorra. 
In the genus Scatarra, the mouth is circular and bor- 
dered, with the margins united. The spires are covered 
with raised edged, slightly oblique, longitudinal ribs. The 
famous wentletrap is the type of the genus. 
Lamark thus defines his genus DeteninuLa: “ Testa 
univalvis subdiscoidea vel abreviato conica, solida, margari- 
tacea, umbilicata; anfractibus subasperis. Apertura rotun- 
data, marginibus orbiculatim connexis.” The T. delphinus 
is the type of the genus. There are many species of tur- 
bines common on our shores, which are excluded by the 
preceding characters from the genera turbo and delphi- 
nula, such as the striatus, cingellus, bryereus and others. 
They are distinctly turreted, with the margins of the mouth 
united, and constitute a genus termed CrnauLa. 
The Turbo terebra of Linnzeus serves as the type of an- 
other genus, termed TurRRITELLA, in which the margins of 
the mouth are disjoined, the spire regularly turreted, and 
the lip emarginated by a sinus. Nearly allied to the pre- 
ceding is the genus PuastaneLua, which Lamark thus de- 
fines: Testa univalvis, ovata vel conica, solida. Apertura 
longitudinalis, ovata, integra; labro simplici acuto. Colu- 
mella levis basi attenuta. Operculum calcareum vel cor- 
neum animali adherens.” 
Perhaps a rigorous examination of the turbines of British 
writers might justify the formation of one or two new gene- 
ra. In the genus Opostomra, the columella is furnished 
with a tooth. The Turbo interstincta, unidentata, plicata, 
Sandivicensis and insculpta of Montagu, are of this genus. 
They have no resemblance in their structure to the Lin- 
nean volute ; although they have been inconsiderately as- 
sociated with them by the authors of the Deseriptive Cata- 
logue. The preceding genera are formed of marine shells 
those that follow live on the land. 
In the genus Cycnostoma, the mouth is circular, with 
united, and often reflected margins. The animal isfurnish- 
ed with an operculum. The 7. elegans of Montagu is the 
only British species of the genus. 
The species which are related to the Turbo bidens per- 
versus and muscorum of Linnzeus, constitute a very natural 
family, which may be termed Pupacea, distinguished by 
the mouth being furnished with teeth or testaceous lami- 
nee, and the last whorl nearly the same or less than the pre- 
ceding. Perhaps the most convenient way of dividing them 
is into two sections, the first including the dextral, and the 
second the sinistral shells. 
The dextral pupacea form two genera. The Pura, as 
originally constructed by Lamark, was equally faulty with 
many of the old Linnzan genera. As it has been restrict- 
ed to include dextral shells, with the animal possessing four 
tentacula, with eyes at the tips of the two longest, it can 
