Although an occasional visitor of our shores, the Bonito, or Stripe-bellied Tunny (_Thynnus pelamys_), which is much inferior in size to the common tunny of the Mediterranean and the Black Sea, is a true ocean-fish, and generally met with at a vast distance from land. It inhabits the warmer seas, of which it is one of the most active and voracious denizens. It is well known to all voyagers within the tropics for the amusement it affords by its accompanying the vessel in its track, and by its pursuit of the flying-fish. But in its turn the predacious Bonito is subject to the persecutions of the huge Sperm-whale, who will often drive whole shoals before him, and crush dozens at a time between his prodigious jaws. The Pelamid (_Thynnus sarda_), which abounds in all districts of the Mediterranean and on both sides of the Atlantic, has but very lately been discovered in the British waters, a single specimen having been caught a few years ago at the mouth of the North Esk. It greatly resembles the species just mentioned in form and mode of life, prowling about the high seas for cephalopods and flying-fishes, and is very commonly confounded with the bonito by sailors, who also give both of them the name of Skip-jacks, expressive of the habit which many of the large Scomberoids have of skimming the surface of the sea, and springing occasionally into the air. [Illustration: Pilot-Fish.--(Naucrates ductor.)] Another member of the mackerel family, the Pilot-Fish (_Naucrates ductor_), easily recognised by the three dark-blue bands which surround its silvery body, will frequently attend a ship during its course at sea for weeks or even months together, most likely to profit by the offal thrown overboard. Regardless of the useful precept, "avoid bad company," it is frequently found attending the white shark, and owes its name to its being supposed to act as a trusty guide or friendly monitor to that voracious monster, sometimes directing it where to find a good meal, and at others warning it when to avoid a dangerous bait. At all events, the pilot-fish is well rewarded for his attendance by snatching up the morsels which are overlooked by his companion, and as he is an excellent swimmer, and probably keeps a good look-out, has but little reason to fear being snatched up himself. "It has been observed," says Yarrell, "that when a shark and his pilot were following a vessel, if meat was thrown overboard cut into small pieces, and therefore unworthy the shark's attention, the pilot-fish showed his true motive of action by deserting both shark and ship to feed at his leisure on the morsels." The family of the anguilliform fishes, characterised by their serpent-like bodies, destitute of ventral fins, and generally covered by a slippery skin, with, in some of the genera, small scales embedded therein, likewise comprises a number of highly interesting and useful species, forming many generic groups.