Sea Shells 
of New Zealand 
Litoral Zone.—Litus, the seashore. That zone or belt 
which lies between high and low-water marks. 
Lunule.—Literally a little moon. A heart-shaped or lancet- 
shaped area in front of the beaks of a bivalve, one-half 
being on each valve. 
Mantle.—A fleshy tunic investing the soft body of a mol- 
lusc, which makes the shell, produces the colour, and 
provides the periostracum or epidermis which covers 
and protects the shell like a skin. 
Nacreous.—Composed of nacre; pearly. (Nacrum, mother 
of pearl). 
Operculum.—A cover or lid, composed of shelly or cal- 
careous matter, or of horny material; it is attached 
to the foot of spiral molluscs, and closes or partially 
closes the entrance when the creatures retire within. 
Pallium.—The mantle (q.v.). 
Parietal (paries, a wall, a partition).—Pertaining to a 
wall, usually referring to that portion of a shell, in 
the neighbourhood of the inner lip of a spiral uni- 
valve. 
Pelagic.—Inhabiting the open seas, like the Violet sea 
snails, and the Spirula. 
Periostracum.—The skin or epidermis, covering the out- 
side surface of shells, well seen in the Pipi. It pro- 
tects the shell from the solvent action of carbonic acid 
gas, especially in fresh-water mollusca. 
Peristome (Peri, around; stoma, the mouth).—The thick- 
ened rim or lip round the mouth of shells, such as 
the Ring shell and the Pawa. 
Radula.—The tongue of univalve shellfish such as Whelks 
and limpets. It is a long ribbon-like organ, furnished 
with hard, sharp teeth. Used for the purpose of rasp- 
ing vegetable matter for food, and, in the carnivorous 
shellfish, for boring holes in the shells of their victims. 
(Radula, a scraper). 
Resilium.—aA resilient piece of cartilage, at the hinge 
of some bivalves, situated in a resilifer, or spoon-like 
pit, and which causes the shell to open, when the con- 
tractile muscles are relaxed. 
Species——All the specimens or individuals which are so 
much alike that we may reasonably believe them 
to have descended from a common stock constitutes 
a species. (Woodward). 
Spire—lIncludes all those whorls of a spiral univalve 
between the apex and the top of the aperture, 
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