HIPPOCAMPUS, or Sea-horse. The small fishes thus named constitute, together with the Pipe-fishes or Syn-gηathi, a distinct order of the class of fishes, that of Lophobranchs or fishes with the gills arranged in tufts. The name “Sea-horse” has been given from the singular horselike shape of the head and fore-part of the body. The head is compressed, and is prolonged into a flat snout, at the end of which opens the small mouth. The eye occupies the same position as in the horse, and the head is joined at an angle to a narrow and curved neck, which posteriorly is dilated into the broader body. As in all the fishes of this order, the body is not covered with soft skin or scales, but encased in a mail composed of hard and tough scutes, which are of a more or less quadrangular shape, and generally armed with tubercles or spines. The tail is long, flexible, and prehensile, without caudal fin. These fishes are very bad swimmers, their locomotion being entirely dependent on the long dorsal fin which slowly propels them by a rapidly undulating screw-like motion; placed in the middle of the back of a body which generally occupies a vertical or oblique position in the water, this organ of locomotion has a propelling power far inferior to that of a terminal caudal fin. By means of their prehensile tail the sea-horses attach themselves to the stems of sea-weed or corals, which they resemble so closely in their outward appearance that it is difficult to distinguish them,—a resemblance which is still more increased in a group of sea-horses fPhyllopteryx) in which many of the spines and tubercles bear long tapering bands like the fronds of sea-weeds. Originally littoral fishes, sea-horses are, nevertheless, frequently found in mid-ocean, attached to floating substances on which ...