CHONDROPTERY'CII, or CARTILACINET, ono of two great sections into which the class of Fishes is divided.
In this section we find species which possess, in most respects, the highest degree of organisation, while others possess tho lowest observed in the class.
The principal character which distinguishes this section from the fishes with true bone (which usually come first in arrangement) is the cartilaginous substance of which the bones are composed, a circum stance arising from tho very small quantity of earthy matter which enters into their composition. This earthy matter, when observed, is found to be disposed in small granules and not in distinct fibres, as in the first section.
The cranium of these Cellos is not divided by true sutures, but Is formed of a single piece : the maxillary and intermaxillary bones are either wanting or rudimentary, and their functions are performed by bones analogous to the palatines, and sometimes the vomer. Many of the vertebrae are often consolidated. The gelatinous substance, which in most fishes fills the intervals between the vertebre (these intervertebral masses being connected only by a small cord), in thin section frequently forms a thick cord, which varies but slightly in diameter.
In the Myxino (Gastrobranchus &sew) no distinct vertebra) are perceivable, their place being occupied by a soft gelatinous tube. In the extraordinary little fish described by Mr. Yarrell in his ' History of British Fishes,' the Lancelet (A nsphio.rus lanceolatus), this part is still more rudimentary, consisting only of a slender transparent column. [13assentossous.] The Chondropteryyii are divided by Cuvier into two orders—those which !MVO their gills free, as in the generality of fishes; and those in which they are fixed—that is, the external edge attached to the akin. In the former of these orders tho species have but one external The massive is amorphous, with a granular or compact structure. It is found in the island of Unst, in Scotland, and sometimes inter spersed with green oxide : it occurs also in France and in North America, especially near Baltimore. Oxide of Chromium has been observed in some adrolites.