Beginning of Essay
There are two classes of fishlike creatures in the Chordate Phylum. The first is Chondrichthyes Class, which comprises mainly of Sharks and Rays. The seconds is the common Bony of the class Ostechithyes. The apparent similarities between each speech are only skin ....

Middle of Essay
.... ancestor’s Placodermi class. The digestion system of a shark contains a “spiral valve” intestinal system, which increases the surface area and lengthens the time food is digested in the unusually short intestine system of a shark. Sharks sexually reproduce. Unlike a shark, rays have flattened bodies so they can hide themselves in the sand at the bottom of any shallow water area and wait for a meal. Rays also have a whiplike tail for defense and jaws, which it uses to crush mollusks and crustaceans. Class Osterrichhthyes has the most separate species of any vertebrate class. Unlike their oceanic cosines Bony fish have a skeleton ma ....