Four sub-families:—
(i.) Thrissopatrinae.—Mouth large; praemaxillaries very small; maxillaries large, with rather narrow supplemental bone, firmly attached to praemaxillaries; branchiostegals about 30; abdomen compressed to an edge, without serration; no lateral line. Thrissopater, from the Gault of Folkestone.
(ii.) Engraulinae.—Mouth moderate or large; praemaxillaries very small; maxillaries large, with narrow supplemental bones, more or less firmly attached to praemaxillaries; branchiostegals 6 to 19; abdomen rounded or more or less compressed, with or without serration; no lateral line. Recent genera: Dussumieria, Etrumeus, Engraulis, Cetengraulis, Heterothrissa, Coilia. Fossil: Spaniodon, Upper Cretaceous.
(iii.) Clupeinae.—Mouth small or moderate; maxillaries freely movable behind the praemaxillaries, usually with large supplemental bones; branchiostegals 5 to 10; abdomen usually serrated; lateral line usually absent. Recent genera: Clupea, Hyperlophus (Diplomystus), Opisthonema, Brevoortia, Pellonula, Clupeichthys, Odaxothrissa, Pellona, Chirocentrodon, Pristigaster, Raconda, Chatoessus. Fossil: Pseudoberyx, Histiothrissa, Scombroclupea, Leptichthys, Upper Cretaceous.
Fig. 341.—Showing the wide range of variation, within the family, of the bones (pm, praemaxillary, m, maxillary) forming the upper border of the mouth. A, Dussumieria; B, Coilia; C, Pellona; D, Chatoessus; E, Chanos. In these semi-diagrammatic figures the orbit is represented of the same size in all, as affording the best term of comparison in judging of the relative development of the bones of the upper jaw.
(iv.) Chaninae.—Mouth small, toothless; maxillaries firmly attached to praemaxillaries; branchiostegals 4, very broad; abdomen rounded or flattened; lateral line distinct. Chanos, recent; Chanoides, Upper Eocene; Prochanos, Cretaceous.
Heralded by the genus Thrissopater,[[647]] which may be regarded as a connecting type between the Elopidae and the Clupeidae, this family is largely represented in Cretaceous times, more abundantly still in the Eocene and Miocene, where Clupea and Engraulis occur in numerous species; Hyperlophus, distinguished from Clupea by the presence of a dorsal serrated ridge similar to the ventral, occurs in the Upper Cretaceous of Syria, Southern Europe, and South America, in the Eocene of North America and Europe, and is represented at the present day on the West Coast of South America and on the coast and in the rivers of New South Wales. About 200 Clupeids are known to live at the present day, mostly marine species, but a few are confined to fresh-waters; none may be termed deep-sea forms; some, like the Allis Shad (Clupea alosa) and Twait Shad (C. finta), are anadromous, ascending rivers to spawn. The range of the family is almost cosmopolitan. Several species are remarkable for the extreme abundance of individuals, as for example the Herring (Clupea harengus), the Pilchard or Sardine (C. pilchardus), and the Anchovy (Engraulis encrasicholus). The Herring inhabits the northern parts of the Atlantic and the seas north of Asia. As Dr. Günther first showed, the so-called "Whitebait" consists chiefly of the fry of Herrings, which, like those of the Sprat (C. sprattus), have a predilection for brackish water. The Anchovy and the Pilchard, on the other hand, seldom if ever enter estuaries. The eggs of the Herring, contrary to those of most British marine food-fishes, are heavy and adhesive, sticking firmly to stones or fixed objects on the sea bottom, whilst those of the Sprat and Pilchard float on the surface. The larvae are long, slender, and transparent. The Sardine, which affords so valuable a fishery on the West Coast of France, is the immature state of the Pilchard, which grows to a length of 10 to 14 inches. Its movements are not yet well understood, and its scarcity during certain years in the waters where it usually swarms has caused periodical crises in an important industry. Ripe Pilchards are mostly found at a considerable distance from the coasts. The Anchovy is especially abundant in the Mediterranean, but it is also regularly fished in Holland, especially in the Zuydersee, where it breeds, as well as in the Mediterranean; it makes only temporary appearances, and has not been observed to spawn, in the English Channel, although eggs have recently been obtained off the coast of North Lancashire.[[648]]
The imperfectly known Cretaceous Crossognathidae (Crossognathus and Scyllaemus), referred by some authors to the Percesoces, should probably be placed with or near the Clupeidae.
Fam. 17. Salmonidae.—Margin of the upper jaw formed by the praemaxillaries and the maxillaries. Supraoccipital in contact with the frontals, but frequently overlapped by the parietals, which may meet in a sagittal suture; opercular bones all well developed. Basis cranii double. Ribs sessile, parapophyses very short or absent; epineurals, sometimes also epipleurals, present. Post-temporal forked, the upper branch attached to the epiotic, the lower to the opisthotic; postclavicle, as usual, applied to inner side of clavicle. A small adipose dorsal fin. Air-bladder usually present, large. Oviducts rudimentary or absent, the ova falling into the cavity of the abdomen before exclusion.