The pike (_Esox lucius_) is smaller than the muskallunge, and is technically best distinguished by the fact that the opercles are naked below, while the cheeks are entirely scaly. The spots and cross-bars in the pike are whitish or yellowish, and always paler than the olive-gray ground color. It is the most widely distributed of all fresh-water fishes, being found from the upper Mississippi Valley, the Great Lakes, and New England to Alaska and throughout northern Asia and Europe. It reaches a weight of ten to twenty pounds or more, being a large strong fish in its way, inferior only to the muskallunge. In England _Esox lucius_ is known as the pike, while its young are called by the diminutive term pickerel. In America the name pickerel is usually given to the smaller species, and sometimes even to _Esox lucius_ itself, the word being with us a synonym for pike, not a diminutive. Of the small pike or pickerel we have three species in the eastern United States. They are greenish in color and banded or reticulated, rather than spotted, and, in all, the opercles as well as the cheeks are fully covered with scales. One of these (_Esox reticulatus_) is the common pickerel of the Eastern States, which reaches a respectable size and is excellent as food. The others, _Esox americanus_ along the Atlantic seaboard and _Esox vermiculatus_ in the middle West, seldom exceed a foot in length and are of no economic importance. Numerous fossil species are found in the Tertiary of Europe, _Esox lepidotus_ from the Miocene of Baden being one of the earliest and the best known; in this species the scales are much larger than in the recent species. The fossil remains would seem to indicate that the origin of the family was in southern Europe, although most of the living species are American. [Illustration: FIG. 152.—Mud-minnow, _Umbra pygmæa_ (De Kay). New Jersey. ] =The Mud-minnows.=—Close to the pike is the family of _Umbridæ_, or mud-minnows, which technically differ from the pikes only in the short snout, small mouth, and weak dentition. The mud-minnows are small, sluggish, carnivorous fishes living in the mud at the bottom of cold, clear streams and ponds. They are extremely tenacious of life, though soon suffocated in warm waters. The barred mud-minnow of the prairies of the middle West (_Umbra limi_) often remains in dried sloughs and bog-holes, and has been sometimes plowed up alive. _Umbra pygmæa_, a striped species, is found in the Eastern States and _Umbra crameri_ in bogs and brooks along the Danube. This wide break in distribution seems to indicate a former wide extension of the range of _Umbridæ_, perhaps coextensive with _Esox_. Fossil _Umbridæ_ are, however, not yet recognized.