Why do the ray genus appear to have contributed to the fable of Sirens?

Because of a certain similarity of the lower part of their head to the human face. Many species have also been dried, and metamorphosed, by a variety of artifices, into supposed basilisks, etc. Although they lay but one egg at a time, they increase so rapidly, that the ocean, in some spots, actually swarms with them. Their eggs have a horny covering with four points, and are called sea-mice. - Blumenhach.

Why is the liver of the skate, cod, and some other fishes, remarkably oily?

Because the rest of their bodies is almost destitute of fat.

Dr. Monro, calculated that the whole gills of a large skate, presented a surface equal to 2,250 square inches; or equal to the whole external surface of the human body.