Fam. 52.--_Scalariidae._ Shell turriculated, with elongated spire;
proboscis short; siphon rudimentary. _Scalaria. Eglisia._ Crossea.
Aclis.
The three following families have neither radula nor jaws, and are
therefore called _Aglossa_. They have a well-developed proboscis which
is used as a suctorial organ; some are abyssal, but the majority are
either commensals or parasites of Echinoderms.
Fam. 53.--_Pyramidellidae._ Summit of spire heterostrophic; a
projection, the mentum, between head and foot; operculum present.
_Pyramidella. Turbonilla. Odostomia_, British. _Myxa._
[Illustration: FIG. 33.--Section of the shell of _Triton_, Cuv. (From
Owen.)
a, Apex.
ac, Siphonal notch of the mouth of the shell.
ac to pc, Mouth of the shell.
w, w, Whorls of the shell.
s, s. Sutures.
Occupying the axis, and exposed by the section, is seen the
"columella" or spiral pillar. The upper whorls of the shell are
seen to be divided into separate chambers by the formation of
successively formed "septa."]
Fam. 54.--_Eulimidae._ Visceral mass still coiled spirally; shell
thin and shining. _Eulima_, foot well developed, with an operculum,
animal usually free, but some live in the digestive cavity of
Holothurians. _Mucronalia_, foot reduced, but still operculate, eyes
present, animal fixed by its very long proboscis which is deeply
buried in the tissues of an Echinoderm, no pseudopallium.
_Stylifer_, the operculum is lost, animal fixed by a large proboscis
which forms a pseudopallium covering the whole shell except the
extremity of the spire, parasitic on all groups of Echinoderms.
_Entosiphon_, visceral mass still coiled; shell much reduced,
proboscis very long forming a pseudopallium which covers the whole
body and projects beyond in the form of a siphon, foot and nervous
system present, eyes, branchia and anus absent, parasite in the
Holothurian _Deima blakei_ in the Indian Ocean.
Fam. 55.--_Entoconchidae._ No shell; visceral mass not coiled; no
sensory organs, nervous system, branchia or anus; body reduced to a
more or less tubular sac; hermaphrodite and viviparous; parasitic in
Holothurians; larvae are veligers, with shell and operculum.
_Entocolax_, mouth at free extremity, animal fixed by aboral orifice
of pseudopallium, Pacific. _Entoconcha_, body elongated and tubular,
animal fixed by the oral extremity, protandric hermaphrodite,
parasitic in testes of Holothurians causing their abortion.
_Enteroxenos_, no pseudopallium and no intestine, hermaphrodite,
larvae with operculum.
Tribe 2.--HETEROPODA. Pelagic Taenioglossa with foot large and
laterally compressed to form a fin.
Fam. 1. _Atlantidae._ Visceral sac and shell coiled in one plane;
foot divided transversely into two parts, posterior part bearing an
operculum, anterior part forming a fin provided with a sucker.
_Atlanta. Oxygyrus._
Fam. 2.--_Carinariidae._ Visceral sac and shell small in proportion
to the rest of the body, which cannot be withdrawn into the shell;
foot elongated, fin-shaped, with sucker, but without operculum.
_Carinaria. Cardiopoda._
Fam. 3.--_Pterotrachaeidae._ Visceral sac very much reduced; without
shell or mantle; anus posterior; foot provided with sucker in male
only. _Pterotrachaea. Firoloida. Pterosoma._
Sub-order 2.--STENOGLOSSA. Radula narrow with one lateral tooth on
each side, and one median tooth or none.
Tribe 1.--RACHIGLOSSA. Radula with a median tooth and a single tooth
on each side of it. Formula 1 : 1 : 1. Rudimentary jaws present.
[Illustration: FIG. 34.--Female _Janthina_, with egg-float (a)
attached to the foot; b, egg-capsules; c, ctenidium (gill-plume); d,
cephalic tentacles.]
Fam. 1.--_Turbinellidae._ Shell solid, piriform, with thick folded
columella; lateral teeth of radula bicuspidate. _Turbinella.
Cynodonta. Fulgur. Hemifusus. Tudicla. Strepsidura._
Fam. 2.--_Fasciolariidae._ Shell elongated, with long siphon;
lateral teeth of radula multicuspidate. _Fasciolaria. Fusus.
Clavella. Latirus._
Fam. 3.--_Mitridae._ Shell fusiform and solid, aperture elongated,
columella folded; no operculum; eyes on sides of tentacles. _Mitra.
Turricula. Cylindromitra. Imbricaria._
Fam. 4.--_Buccinidae._ Foot large and broad; eyes at base of
tentacles; operculum horny. _Buccinum. Chrysodomus. Liomesus.
Cominella. Tritonidea. Pisania. Euthria. Phos. Dipsacus._
Fam. 5.--_Nassidae._ Foot broad, with two slender posterior
appendages; operculum unguiculate. _Nassa_, marine, British.
_Canidia_, fluviatile. _Bullia._
Fam. 6.--_Muricidae._ Shell with moderately long spire and canal,
ornamented with ribs, often spiny; foot truncated anteriorly.
_Murex_, British. _Trophon_, British. _Typhis. Urosalpinx.
Lachesis._
Fam. 7.--_Purpuridae._ Shell thick, with short spire, last whorl
large and canal short; aperture wide; operculum horny. _Purpura_,
British. _Rapana. Monoceros. Sistrum. Concholepas._
Fam. 8.--_Haliidae._ Shell ventricose, thin and smooth, with wide
aperture; foot large and thick, without operculum. _Halia._
Fam. 9.--_Cancellariidae._ Shell ovoid, with short spire and folded
columella; foot small, no operculum; siphon short. _Cancellaria._
Fam. 10.--_Columbellidae._ Spire of shell prominent, aperture
narrow, canal very short, columella crenelated; foot large.
_Columbella._
Fam. 11.--_Coralliophilidae._ Shell irregular; radula absent; foot
and siphon short; sedentary animals, living in corals.
_Coralliophila. Rhizochilus. Leptoconchus. Magilus. Rapa._
Fam. 12.--_Volutidae._ Head much flattened and wide, with eyes on
sides; foot broad; siphon with internal appendages. _Valuta.
Guivillea. Cymba._
Fam. 13.--_Olividae._ Foot with anterior transverse groove; a
posterior pallial tentacle; generally burrowing. _Olivia. Olivella.
Ancillaria. Agaronia._
Fam. 14.--_Marginellidae._ Foot very large; mantle reflected over
shell. _Marginella. Pseudomarginella._
Fam. 15.--_Harpidae._ Foot very large; without operculum; shell with
short spire and longitudinal ribs; siphon long. _Harpa._
Tribe 2.--TOXIGLOSSA. No jaws. No median tooth in radula. Formula: 1 :
0 : 1. Poison-gland present whose duct traverses the nerve-collar.
Fam. 1.--_Pleurotomatidae._ Shell fusiform, with elongated spire;
margin of shell and mantle notched. _Pleurotoma. Clavatula.
Mangilia. Bela. Pusionella. Pontiothauma._
Fam. 2.--_Terebridae._ Shell turriculated, with numerous whorls;
aperture and operculum oval; eyes at summits of tentacles; siphon
long. _Terebra._
Fam. 3.--_Conidae._ Shell conical, with very short spire, and narrow
aperture with parallel borders; operculum unguiform _Conus._