This genus derived its name from its resemblance to a top.
The shells are marine, found in almost all parts of the world; some are
smooth, but the greater number are covered, with knobs, spines,
tuberculations, or undulations.
The long spines on the margin of the T. Solaris are placed at regular
distances, and resemble the rays of the sun. Many, when decorticated,
look like mother-of-pearl; others have a splendid metallic lustre. The
T. agglutinans possesses the faculty of covering itself with extraneous
substances, such as stones, corals, fragments of shells, &c. Of this
species there are two kinds, which, though conchologically known only by
one name, are familiarly known by two; the Conchologist and the
Mineralogist; the former so called from being loaded with shells, and
the latter with stones, &c. Sometimes the Conchologist is loaded with
corals only, and then is called the Zoologist.
Shell thick, generally pearly, shaped like a top, spire sometimes
depressed, sometimes elevated and pointed at the summit, sharp or
carinated at its circumference, umbilicated or not; aperture depressed,
angular or sub-angular, sometimes heart-shaped, with edges disunited;
the right sharp; the columella arched, twisted, and often projecting
forward; operculum horny, thin, with numerous spiral whorls, narrow, and
increasing a little from the centre to the circumference.
Trochus imperialis.
T. longispina.
T. solaris.
T. Indicus.
T. radians.
T. pileus.
T. calyptræformis.
T. fimbriatus.
T. brevispina.
T. rotularius.
T. stella.
T. stellaris.
T. niloticus.
T. pyramidalis.
T. noduliferus.
T. cærulescens.
T. obeliscus.
T. virgatus.
T. asperatus.
T. rhodostomus.
T. spinulosus.
T. costulatus.
T. inermis.
T. agglutinans.
T. cælatus.
T. tuber.
T. magus.
T. merula.
T. argyrostomus.
T. Cookii.
T. conuloides.
T. conulus.
T. jujubinus.
T. Javanicus.
T. annulatus.
T. doliarius.
T. maculatus.
T. granosus.
T. squarrosus.
T. incrassatus.
T. flammulatus.
T. elatus.
T. marmoratus.
T. Mauritianus.
T. imbricatus.
T. triserialis.
T. crenulatus.
T. asperulus.
T. acutus.
T. concavus.
T. lineatus.
T. zizyphinus.
T. granulatus.
T. granatum.
T. moniliferus.
T. iris.
T. ornatus.
T. bicingulatus.
T. calliferus.
T. umbilicaris.
T. undatus.
T. Pharaonis.
T. sagittiferus.
T. carneolus.
T. cinerarius.
T. excavatus.
T. nanus.
T. pyramidatus.
T. erythroleucos.
_T. imperialis._ The imperial Trochus. Pl. 23, fig. 6.
Species umbilicated, spire very depressed, sharp and radiated at their
circumference by the preservation of an angular canal from the middle of
the right margin. This species is rare and beautiful, found in
New-Zealand.
_T. zizyphinus._ The livid Trochus.
Species with strong transverse striæ; colour livid, with undulated
streaks of red or brownish carnation.
_T. agglutinans._ The agglutinating or Carrier Trochus.
Species umbilicated, with spire very depressed; the base much enlarged,
and as if excavated by the large projection of the angle of the right
edge, which advances much beyond the rounded columellar edge; generally
covered with shells, stones, or coral.
_T. niloticus._ The large marble Trochus.
Species not umbilicated, conical, with base flat and circular; the
columella twisted; the aperture very angular.
_T. obeliscus._ The obelisk Trochus.
Species not umbilicated, conic, elevated, flat and circular base; the
termination of the columella strongly twisted, but passing down by the
margin, appearing sloped by the advance of an internal longitudinal
plait.
_T. iris._ The iris Trochus.
Species not umbilicated, conic, base oblique; aperture large, slightly
angular; the columella twisted, and forming a kind of tooth at its
termination.
_T. granulatus._ The granulated Trochus.
Conic, imperforate at the base, spirally granulated and not marginated
at the edges of the volutions; body swelling out; spire tapering
abruptly; apex acute, flesh-coloured.
_T. umbilicaris._ The umbilicated Trochus.
Shell conico-convex, rather flat, rounded at the top; apex depressed,
volutions sub-marginate; striated spirally; aperture compressed and
angular; umbilicus large, extending to the apex; colour whitish.