The extinct family of Pachyrhizodontidæ is perhaps allied to the Elopidæ. Numerous species of Pachyrhizodus are found in the Cretaceous of southern England and of Kansas.
The Albulidæ.—The Albulidæ, or lady-fishes, characterized by the blunt and rounded teeth, are found in most warm seas. Albula vulpes is a brilliantly silvery fish, little valued as food. The metamorphosis (see Fig. 112, Vol. I) which the larva undergoes is very remarkable. It is probably, however, more or less typical of the changes which take place with soft-rayed fishes generally, though more strongly marked in Albula and in certain eels than in most related forms. Fossils allied to Albula, Albula oweni, Chanoides macropomus, are found in the Eocene of Europe; Syntegmodus altus in the Cretaceous of Kansas. In Chanoides, the most primitive genus, the teeth are much fewer than in Albula. Plethodus and Thryptodus, with peculiar dental plates on the roof and floor of the mouth, probably constitute a distinct family, Thryptodontidæ. The species are found in European and American rocks, but are known from imperfect specimens only.
Fig. 31.—The Lady-fish, Albula vulpes (Linnæus). Florida.
The Chanidæ.—The Chanidæ, or milkfishes, constitute another small archaic type, found in the tropical Pacific. They are large, brilliantly silvery, toothless fishes, looking like enormous dace, swift in the water, and very abundant in the Gulf of California, Polynesia, and India. The single living species is the Awa, or milkfish, Chanos chanos, largely used as food in Hawaii. Species of Prochanos and Chanos occur in the Cretaceous, Eocene, and Miocene. Allied to Chanos is the Cretaceous genus Ancylostylos (gibbus), probably the type of a distinct family, toothless and with many-rayed dorsal.
Fig. 32.—Milkfish, Chanos chanos (L.). Mazatlan.
Fig. 33.—Mooneye, Hiodon tergisus Le Sueur. Ecorse, Mich.
The Hiodontidæ.—The Hiodontidæ, or mooneyes, inhabit the rivers of the central portion of the United States and Canada. They are shad-like fishes with brilliantly silvery scales and very strong sharp teeth, those on the tongue especially long. They are very handsome fishes and take the hook with spirit, but the flesh is rather tasteless and full of small bones, much like that of the milkfish. The commonest species is Hiodon tergisus. No fossil Hiodontidæ are known.