Page:Natural History, Fishes.djvu/256

242 The Family consists of one hundred and eighty known species, scattered over all parts of both oceans. Almost all of them are marine, and few of these ascend rivers. Generally they are of small size, comparatively few exceeding our own well-known Herring; yet to this rule the Shad of our rivers is an exception, which grows to three feet in length, and the genus Megalops of the tropical seas is found to attain twelve feet.

The food of such species as we are familiar with consists principally of minute crustaceous animals, and, it is probable, from the minuteness of the teeth in the Family, that the food is in general small.

Some of our best-known and most valuable fishes are contained in this genus, as the Pilchard, Herring, Sprat, and Whitebait, not to reckon the Shads and the Anchovy, which are now placed in separate genera. Its distinctive characters are that the mouth is small, obliquely vertical; the teeth very minute or absent, the jaws nearly equal, not notched; the belly line compressed to an edge, sharp, and generally serrated: the dorsal fin situated above the ventrals; the latter about equal to the pectorals, and both small; the caudal forked: the body is covered with large thin scales, removed with little force.

The Herrings are believed to be wholly carnivorous; and, as we have already observed, minute Crustacea form a large portion of their sustenance. Mr. Yarrell observes of the Pilchard, "I have found their stomachs crammed each with