All these parts are supported by plates or ossicles of crystalline carbonate of lime.
I); and since it was believed that the stem always grew by addition of ossicles immediately below the infrabasals, it was inferred that this pentagonal plate was the centro-dorsal in its primitive position, as though the wine-glass had been evolved from a tumbler by pulling the bottom out to form the foot.
Ossicles somewhat resembling large coffee-berries had been previously found in association with the bones of Mylodon, and in Glossotherium nearly similar ossicles occur embedded on the inner side of the thick hide.
Thyng, who has carefully reviewed all the other theories, the balance of evidence tends to show that the quadrate has been taken up into the inner ear, where it is represented among the auditory ossicles by the incus.
The resemblance of the flooring-plates to the ambulacral ossicles of a starfish is so exact that one can explain it only by supposing similar relations of the water-canals and their branches (podia).