So obscure is the ichthyology of the ancients, or so little care has been taken to explain it, that the question whether our carp were known to Aristotle, Pliny, and their contemporaries, cannot with any great degree of probability be determined. Besides, that subject is attended with much greater difficulties than the natural history of quadrupeds. Among four-footed animals there is a greater variety in their bodily conformation, which at any rate strikes the eye more, and can be more easily described than that of fishes, which in general are so like in shape, that an experienced systematic naturalist finds it sometimes difficult to determine the characters of the genera and species. It is not surprising therefore that the simple descriptions of the ancients, or rather the short accounts which they give us of fish, do not afford information sufficient to enable us to distinguish with accuracy the different kinds. Quadrupeds may terrify us by their ferocity, or endeavour to avoid us by shyness and craft; but it is still possible to observe their sexes, their age, and their habits, and to remark many things that are common to one or only a few species. Fishes, on the other hand, live in an element in which we cannot approach them, and which for the most part conceals them from our observation. The chase, since the earliest periods, and in modern times more than formerly, has been the employment of idle persons, who bestow upon it greater attention the fewer those objects are which can attract their curiosity or employ their minds: but fishing has almost always been the laborious occupation of poor people, who have no time to make observations, as they are obliged to follow it in order to find a subsistence; and mankind in general seldom see fish except on their tables or in collections of natural history. On this account those properties of fish by which their species could be determined, were less known. The descriptions of four-footed animals which have been handed down to us from the time of the Greek and Roman writers, give us, at any rate, some information; but from those of fishes, which are more uncommon, we can scarcely derive any; unless one were as acute or easy of belief as many collectors of petrefactions, who imagine that they can distinguish each species of fish in the impressions which they see in stones. More however might be done towards elucidating the ichthyology of the ancients than has hitherto been attempted. It would be necessary only to make a beginning by collecting the species and names which can with certainty be determined, together with the authorities, and separating them from the rest; and an abstract should be formed of what is said in the ancients respecting the unknown species, or whatever may in any measure serve to make us acquainted with them; but mere conjectures ought never to be given as proofs, nor ought the opinions of commentators, or the explanations of dictionaries to be adopted