The Baikal Cods: Comephoridæ.—The family of Comephoridæ includes Comephorus baikalensis, a large fresh-water fish of Lake Baikal in Siberia, having no near affinities with any other existing fish, but now known to be a mail-cheek fish related to the Cottidæ. The body is elongate, naked, with soft flesh and feeble skeleton. The mouth is large, with small teeth, and the skull has a cavernous structure. There are no ventral fins. The spinous dorsal is short and low, the second dorsal and anal many-rayed, and the pectoral fins are excessively long, almost wing-like; the vertebræ number 8 + 35 = 43, and unlike most fresh-water fishes, the species has no air-bladder. Little is known of the habits of this singular fish. Another genus is recently described under the name of Cottocomephorus.

Suborder Craniomi: the Gurnards, Triglidæ.—A remarkable offshoot from the Pareioplitæ is the suborder of gurnards, known as Craniomi (κράνιον, skull; ὤμος, shoulder). In these fishes the suborbital stay is highly developed, much as in the Agonidæ, bony externally and covering the cheeks. The shoulder-girdle is distorted, the post-temporal being solidly united to the cranium, while the postero-temporal is crowded out of place by the side of the proscapula. In other regards these fishes resemble the other mail-cheek forms, their affinities being perhaps closest with the Agonidæ or certain aberrant Cottidæ as Ereunias.

In the true gurnards or Triglidæ the head is rough and bony, the body covered with rough scales and below the pectoral fin are three free rays used as feelers by the fish as it creeps along the bottom. These free rays are used in turning over stones, exploring shells and otherwise searching for food. The numerous species are found in the warm seas. In Europe, the genus Trigla, without palatine teeth and with the lateral line armed, is represented by numerous well-known species. Trigla cuculus is a common form of the Mediterranean. Chelidonichthys, similar to Trigla but larger and less fully armed, is found in Asia as well as in Europe. Several species occur in the Mediterranean. Chelidonichthys kumu is a common species in Japan, a large fish with pectorals of a very brilliant variegated blue, like the wings of certain butterflies.

Lepidotrigla, with larger scales, has many species on the coasts of Europe as well as in China and Japan. Lepidotrigla alata, a red fish with a peculiar bony, forked snout, is common in Japan. The American species of gurnards, having teeth on the palatine, belong to the genus Prionotus. Northward these fishes, known as sea-robins, live along the shores in shallow water. In the tropics they descend to deeper water, assuming a red color. Prionotus carolinus is the commonest species in New England. Prionotus strigatus, the striped sea-robin, and Prionotus tribulus, the rough-headed sea-robin, are common species along the Carolina coast. None have much value as food, being dry and bony. Numerous fossil species referred to Trigla are found in the Miocene. Podopteryx, from the Italian Miocene, with small pectorals and very large ventrals, perhaps belongs also to this family, but its real affinities are unknown.

The Peristediidæ.—The Peristediidæ are deep-water sea-robins, much depressed, with flat heads, a bony coat of mail, and two free feelers on the pectoral fin instead of three. The species of Peristedion are occasionally taken with the dredge. Peristedion cataphractum is rather common in Europe. The extinct Peristedion urcianense is described from the Pliocene of Orciano, Tuscany.

The Flying Gurnards: Cephalacanthidæ.—The flying gurnards, Cephalacanthidæ, differ in numerous respects and are among the most fantastic inhabitants of the sea. The head is short and bony, the body covered with firm scales, and the very long, wing-like pectoral fin is divided into two parts, the posterior and larger almost as long as the rest of the body. This fin is beautifully colored with blue and brownish red. The first spine of the dorsal fin is free from the others and more or less prolonged. The few species of flying gurnard are much alike, ranging widely in the tropical seas, and having a slight power of flight. The flying robin, or batfish, called in Spanish volador or murcielago, Cephalacanthus volitans, is common on both coasts of the Atlantic, reaching a length of eighteen inches. Cephalacanthus peterseni is found in Japan and Cephalacanthus orientalis in the East Indies, Japan, and Hawaii. The immature fishes have the pectoral fins much shorter than in the adult, and differ in other regards. Cephalacanthus pliocenicus occurs in the Lower Pliocene of Orciano, Tuscany.

Petalopteryx syriacus, an extinct flying gurnard found in the Cretaceous of Mount Lebanon, is an ally of Cephalacanthus. The body is covered with four-angled bony plates, and the first (free) spine of the dorsal is enlarged.