The sclerites of " Chrysomallon squamiferum " are mainly proteinaceous ( conchiolin is a complex protein ); in contrast, the sclerites of chitons are mainly calcareous.
12.
The presence of a subperipheral belt much the same as in " Protatlanta souleyeti ", on the other hand, demonstrates that a conchiolin keel has been present in this species.
13.
The shell's structure is distinctive : sinuous bands of blue, green, and rose iridescence are delineated by dark brown lines of conchiolin, a proteinaceous material that holds the shell together.
14.
Some land snails ( especially the taxa that have become adapted to living on acidic soils ) have very thin, transparent, tan-colored shells, even as adults, and those shells are composed entirely of conchiolin.
15.
Conchiolin serves as a relatively flexible, crack-deflecting aggregate particles; its strength and the strong bonding of perlucin can in some cases ( such as in the formation of nacre ) give the finished material an impressive level of toughness.
16.
Instead, they gradually increase in size at one edge, called the growing edge, as crystals of mineral salts are secreted by a large, thin, enveloping flap of tissue called the mantle and laid down in a framework of a hornlike substance called conchiolin.
17.
As well as providing a matrix into which the hard calcium carbonate part of the shell is precipitated, many species of mollusks ( such as the land snail shown above ) also have an outer shell layer called the periostracum which is composed of the protein conchiolin.
18.
In habitats where there is not enough calcium carbonate to build a really solid shell, such as on some acidic soils on land, there are still various species of slugs, and also some snails with a thin translucent shell, mostly or entirely composed of the protein conchiolin.
19.
The mollusk's mantle ( protective membrane ) deposits layers of calcium carbonate ( CaCO 3 ) in the form of the mineral aragonite or a mixture of aragonite and calcite ( polymorphs with the same chemical formula, but different crystal structures ) held together by an organic horn-like compound called conchiolin.
20.
Not all gastropods have opercula, but in the great majority of those that do have one, the operculum is corneous . ( However in several genera within a few families including the marine Naticidae and the terrestrial Pomatiidae, the operculum is primarily calcareous, in other words mostly made of calcium carbonate . ) Corneous opercula are made out of the protein conchiolin.
