Page:EB1911 - Volume 11.djvu/534

Fam. 29.—Vermetidae. Animal fixed by the shell, the last whorls of which are not in contact with each other; foot small; two anterior pedal tentacles. Vermetus. Siliquaria.

Fam. 30.—Caecidae. Shell almost completely uncoiled, in one plane, with internal septa. Caecum, British.

Fam. 31.—Turritellidae. Shell very long; head large; foot broad. Turritella, British. Mesalia. Mathilda.

Fam. 32.—Struthiolariidae. Shell conical; aperture slightly canaliculated; siphon slightly developed. Struthiolaria.

Fam. 33.—Chenopodidae. Shell elongated; aperture expanded; siphon very short. Chenopus, British. Alaria, Spinigera, Diartema, extinct.

Fig. 31.—Shell of Crucibulum, seen from below so as to show the inner whorl b, concealed by the cap-like outer whorl a.

Fam. 34.—Strombidae. Foot narrow, compressed, without sole. Strombus. Pteroceras. Rostellaria. Terebellum.

Fam. 35.—Xenophoridae. Foot transversely divided into two parts. Xenophorus. Eotrochus, Silurian.

Fam. 36.—Capulidae. Shell conical, not coiled, but slightly incurved posteriorly; a tongue-shaped projection between snout and foot. Capulus. Thyca, parasitic on asterids. Platyceras, extinct.

Fam. 37.—Hipponycidae. Shell conical; foot secreting a ventral calcareous plate; animal fixed. Hipponyx. Mitrularia.

Fam. 38.—Calyptraeidae. Shell with short spire; lateral cervical lobes present; accessory genital glands. Calyptraea, British. Crepidula. Crucibulum.

Fam. 39.—Naricidae. Foot divided into two, posterior half bearing the operculum; a wide epipodial velum; shell turbinated. Narica.

Fam. 40.—Naticidae. Foot large, with aquiferous system; propodium reflected over head; eyes degenerate; burrowing habit. Natica, British. Amaura. Sigaretus.

Fam. 41.—Lamellariidae. Shell thin, more or less covered by the mantle; no operculum. Lamellaria. Velutina. Marsenina, Oncidiopsis, hermaphrodite.

Fam. 42.—Trichotropidae. Shell with short spire, carinate and pointed. Trichotropis.

Fam. 43.—Seguenziidae. Shell trochiform, with canaliculated aperture and twisted columella. Seguenzia, abyssal.

Fam. 44.—Janthinidae. Shell thin; operculum absent; tentacles bifid; foot secretes a float; pelagic. Janthina. Recluzia.

Fam. 45.—Cypraeidae. Shell inrolled, solid, polished, aperture very narrow in adult; short siphon; anus posterior; osphradium with three lobes; mantle reflected over shell. Cypraea. Pustularia. Ovula. Pedicularia, attached to corals. Erato.

Fam. 46.—Tritonidae. Shell turriculated and siphonated, thick, each whorl with varices; foot broad and truncated anteriorly; pallial siphon well developed; proboscis present. Triton. Persona. Ranella.

Fig. 32.—Animal and shell of Ovula.
b,	Cephalic tentacles.
d,	Foot.
h,	Mantle-skirt, which is naturally carried in a reflected condition so as to cover the sides of the shell.

Fam. 47.—Columbellinidae. All extinct.

Fam. 48.—Cassididae. Shell ventricose, with elongated aperture, and short spire; proboscis and siphon long; operculum with marginal nucleus. Cassis. Cassidaria. Oniscia.

Fam. 49—Oocorythidae. Shell globular and ventricose; aperture oval and canaliculated; operculum spiral. Oocorys, abyssal.

Fam. 50.—Doliidae. Shell ventricose, with short spire, and wide aperture; no varices and no operculum; foot very broad, with projecting anterior angles; siphon long. Dolium. Pyrula.

Fam. 51.—Solariidae. Solarium. Torinia. Fluxina.

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.

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.

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.