The relations and systematic position of this group of fishes, so important from an economic point of view, have been, and are still, a subject of contention among ichthyologists. Having no spines to their fins, the Gadids used, in Cuvierian days, to be associated with the herrings, Salmonids, pike, and such like, in the artificially conceived order of Malacopterygians or soft-finned fishes. But, on the ground of their air-bladder being closed, or deprived of a pneumatic duct communicating with the digestive canal, such as is characteristic of the true Malacopterygians and of most other " soft-finned " fishes, they were removed from them and placed with the flat fishes, or Pleuronec-tids, in a sub-order, " Anacanthini" regarded as intermediate in position between the Acanthoptery-gians, or spiny-finned fishes, and the Malacopterygians. It has, however, been shown, I should even say conclusively proved, that the flat fishes bear no relationship to the Gadids; they are, in the opinion of the writer, most nearly akin to the John Dories, or Zeidae, with which they are connected by an extinct type, Amphistium, from the Eocene, giving us an idea of what the common ancestor of these forms, so different in appearance at the present day, must have been like. Although we have no hesitation in removing the Gadids from the vicinity of the flat fishes or of the Malacopterygians, we find it difficult to suggest which group the Anacan-thini, now restricted to the Gadidae and the Macru-ridae, may have been derived from; in trying to reconstitute the phylogeny of the bony fishes, we should probably seek for their direct ancestors among the sub-order Haplomi, including the pike and the numerous allies of the Bombay duck (Harpodon), the Scopelidae, rather than from any of the Acanthopterygians, as was at one time believed.
Any of our readers who might feel interested in the recent views on the relationships of the Gadidae, should refer to the paper by the writer in the Annals and Magazine of Natural History, vol. x. 1902, p. 295, and to another by Mr. C. Tate Regan in the same journal, vol. xi. 1903, p. 459.
The Gadidae may be described as Teleosts with closed air-bladder, with all the fin-rays articulated, made up of distinct segments, and flexible, with a perfectly symmetrical caudal fin which is not supported by an enlarged fan-shaped bone, and with the ventral fins inserted in advance of the pectoral fins, and not connected with the bones of the shoulder-girdle otherwise than by ligament. The scales are small, smooth, and thin, and the chin is frequently provided with a fleshy appendage or barbel. The very forward position of the ventral fins serves to distinguish these fishes from all other piscine members of our fauna in which the body is symmetrical and the fin-rays are all articulated and flexible.
About 120 species are distinguished, mostly marine, many being adapted to life at great depths; all are carnivorous. They inhabit chiefly the northern seas, but many abyssal forms occur between the Tropics and in the southern parts of the Atlantic and Pacific. They are represented in our waters by eight genera, which may be distinguished in the following manner:-
1. Gadus. Three dorsal and two anal fins.
2. Merlucciujy hake. Two dorsal fins, the front one short, the hind one long; a single, long anal fin.
A. Two dorsal fins, the front one short but well developed, the hind one long; a single, long anal fin.
3. Molvaling. Ventral fins with several rays; dorsal and anal not quite reaching the caudal; enlarged teeth in the lower jaw.
4. Lota burbot. Ventral fins with several rays; dorsal and anal fins reaching the caudal; teeth all small.
5. Phycis, fork-beard. Ventral fin reduced to a bifid filament.
B. Two dorsal fins, the front one rudimentary; a single, long anal fin.
6. Raniceps, tadpole fish. No nasal barbels.
7. Onus (Motelld)y rocklings. Nasal barbels.
C. A single dorsal and a single anal fin, both very long.
8. Brosmius, tusk or torsk.
The burbot is our only fresh-water representative of the Gadidse.
Only the first genus, of which the cod is the * type, need occupy us here as containing two fishes, the coal-fish and the pollack, which afford sport to anglers. It is represented on our coasts by eight species, some of which are sufficiently nearly allied to offer some difficulties in their determination. These difficulties will, we think, disappear if use be made of the following synopsis or key which we have drawn up for their easy identification.
I. Base of first anal fin not or but slightly longer than that of the second dorsal fin; upper jaw projecting more or less beyond the lower.
1. G. morrhua, cod. Mental barbel at least half as long as the eye; first anal fin with 17 to 20 rays ; lateral line whitish.
2. G. aglefinus, haddock. Mental barbel very short; first anal fin with 22 to 25 rays; lateral line dark.
3. G. minutuSy power or poor cod. Mental barbel as long as or a little shorter than the eye; anal fin with 25 to 29 rays.
II. Base of first anal fin considerably longer than that of the second dorsal.
A. Upper jaw projecting a little beyond the lower; a dark spot at the root of the pectoral fin.
4. G. merlangusy whiting. No barbel; no dark bars.
5. G. luscus, bib or pout. A mental barbel, nearly as long as the eye; body deep, with more or less distinct dark bars.
B. Lower jaw projecting more or less beyond the upper; usually a dark spot in the axil of the pectoral fin.
6. G. virens, coal-fish. A small mental barbel, sometimes rudimentary; vent below the posterior half of the first dorsal fin.
7. G. pollachtHSy pollack. No barbel; lower jaw strongly projecting; vent below the anterior half of the first dorsal fin.
8. G. poutassou, poutassou. No barbel; second dorsal fin not longer than the first; vent before the vertical of the first dorsal fin.