GLOSSARY 
Adductor Muscles.—The muscles of bivalve molluscs, 
which are attached to the valves internally, one at either 
end. They adduct or draw together the two portions 
of the shell, and so close it. The scars, or points of 
attachment, are well marked in the Pipi. 
Byssus.—The beard, or small bundle of threads, by which 
some bivalves attach themselves to rocks, etc. 
Chiton.—Multivalve mollusca. Animals with a shelly in- 
tegument, consisting of eight separate pieces overlap- 
ping each other like plates of armour. 
Columella.—The central pillar of a univalve, round which 
the whorls are built, extending from the apex to the 
base of the shell. A portion of the columella is seen 
at the aperture of most spiral univalves. 
Escutcheon.—An elongated depression on the valves of a 
bivalve shell, situated behind the beaks and enclosing 
the ligament. Not always present. 
Fauna.—A collective term for all the different forms of 
animal life peculiar to a district, a country, or belong- 
ing to the same epoch. 
Genus.—A number of species closely allied to each other, 
and grouped together for convenience in classification. 
(Plural, genera). 
Hinge Teeth.—Small projections at the hinge of bivalve 
shells fitting into corresponding depressions on the op- 
posing valve to prevent lateral displacement when the 
valves are closed, 
Incremental Lines.—Marks on the shell indicating growth. 
The shell grows at set periods with intervals of absolute 
rest. 
Lamina.—A thin plate; lamella being the diminutive form 
of the same. 
Laminarian Zone.—The zone or belt below low-water 
mark, and including the bed of the ocean in which sea- 
weed grows. 
Ligament.—A tough, fibrous structure attached to both 
valves and holding them securely together. 
erat fine ridge between two small furrows. (Plural, 
we), | 
121 
Sea Shells 
of New Zealand 
