Heterocercal
a term introduced by Agassiz to designate the unsymmetrical tail of elasmobranch and most ganoid fishes, in which the vertebral axis is bent upward in the tail, making the upper lobe much the larger.
HETEROPODA (-op'ō-dä), an order of marine mollusks, the most highly organized of the Gasteropoda. In this order the foot is compressed into a vertical muscular lamina, serving for a fin, and the gills, when present, are collected into a mass on the hinder part of the back. The chief genera are Carinaria and Firola.